DEAR MISS MANNERS: How often should a child have a birthday party during his or her childhood?

GENTLE READER: How often does the child have a birthday?

Perhaps you are confused by Miss Manners' rule that limits major adult celebrations to only three in a lifetime. This is so as not to overtax one's friends and appear childishly indulgent.

Miss Manners is more generous with actual children. She permits them a birthday party every year -- at their parents' discretion, and as long as there is no registry nonsense.

So then the question is, at what age is childhood finished? While she is inclined to leave this to the philosophers, her guess would be 18. Thus if a huge occasion is made of the 21st birthday, the next two could be scheduled at ages 50 and 100.

DEAR MISS MANNERS: When I have been in waiting rooms or similar settings and another person sitting next to me begins a conversation, I will acknowledge them and respond. However, there have been times when the other person will become negative and make comments that I considerate inappropriate or offensive to others, whether or not those others are there.

For instance, a lady sitting near me one day last week began complaining about people who do not speak English, and saying, "Don't you agree?" The next day, a man sitting next to me was saying that all young persons are lazy and expect a handout.

People have picked me out in a group as someone who wants to hear their opinions on politics, religion and just about everything else. Please tell me how I can politely get out of being drawn into these negative diatribes.

GENTLE READER: By not speaking to strangers, as you were once taught. They sometimes say strange things.

Rebuffing a talker in a waiting room or on an airplane cannot be as harsh as, for example, reacting to a stranger who has made an invitation to you on the street. In that case, Miss Manners advises walking away, if not calling the police.

But chatting with people in a confined situation such as a waiting room or airplane is optional. You can break in when the conversation turns unpleasant, or even tedious, by the same method for heading it off entirely: "Forgive me, but I can't talk right now."

DEAR MISS MANNERS: Now that my pregnancy is showing, many women will greet me with a short congratulations and then launch into some very frightening stories. Normally, I try to say, "Pardon me for interrupting, but I'm afraid you have me confused with someone else. I'm sure you would not want to share such a personal story with a complete stranger."

This works well with strangers, but I am at a loss for what to say to co-workers and acquaintances. Is there a polite way I can stop them from telling me their childbirth horror stories?

GENTLE READER: Pregnant ladies are so susceptible to sudden bouts of nausea that no one could blame you if you had to excuse yourself the next time you got whiff of a gruesome tale. Miss Manners suggests doing this often enough that they will catch on, but if they don't, you won't be around long enough to find out.

(Please send your questions to Miss Manners at her website, www.missmanners.com; to her email, dearmissmanners@gmail.com; or through postal mail to Miss Manners, Universal Uclick, 1130 Walnut St., Kansas City, MO 64106.)

DEAR MISS MANNERS: I just received a sharp rebuke from a co-worker for sending him a personal email (following up on a prior conversation) at 5:45 in the morning. His reply stated only that "this exchange should not occur before 7 a.m."

I was taken aback by the tone of his reply. I have never exchanged emails with him outside of business hours before. Presumably, his smartphone alerts him of incoming email and my message disturbed his sleep.

I hadn't anticipated this -- I may be old-fashioned, but I still think of email as a desktop activity. Should I apologize for this apparent intrusion?

GENTLE READER: It used to be that surprise, late-night house calls were understood to be limited to those who could expect to be welcomed with open arms. Exceptions were made for emergencies, warrants and comic figures in Shakespeare plays.

But nocturnal knocks on the door and emails are not the same thing. You did not expect your co-worker instantly to act upon -- or even to see -- the early-morning email, any more than you would have expected an immediate response to a posted letter.

That the mail came early and set the dog barking, which in turn woke up the baby, who toddled down the stairs to the kitchen, terrifying grandma, who spilled her coffee, is not your responsibility.

That said, the best answer to your co-worker is to apologize and gently say that you were having the same problem until you discovered that it was possible to mute the sound announcing new emails on your phone.

DEAR MISS MANNERS: Is it necessary to bring the hostess of a potluck family dinner a hostess gift? Or is my contribution (as per her request), which is often more food than the hostess herself prepares, a hostess gift enough?

GENTLE READER: Hostess? What hostess?

Miss Manners has trouble thinking of someone who orders catered food from you as a hostess. And while you should not expect to be tipped if you also partook of these meals, the optional courtesy of another contribution is unnecessary.

DEAR MISS MANNERS: Due to health problems such as migraines, I am sometimes forced to cancel doctor appointments at the last minute.

When this happens, should I give a brief apology over the phone, send a written apology, or assume that the health professionals go on with their day relatively unaffected by my absence?

GENTLE READER: While it is reasonable to assume that doctors are familiar with -- and perhaps even sympathetic to -- the effects of illness, Miss Manners can assure you that they do not go on with the day unaffected by your absence.

They have been hit hard by the growing societal disregard for the commitment implicit in scheduling an appointment. Most medical offices now call beforehand to remind patients to show up. And an increasing number are registering their displeasure with absenteeism by charging fees for last-minute cancellations.

You do not want to be confused with patients who offer an invented illness to cover a less defensible reason ("I really don't feel like traipsing all the way downtown today"). A handwritten note of apology will reassure your doctor that you value her time. She is the last person you want suspecting you of feigning illness.

(Please send your questions to Miss Manners at her website, www.missmanners.com; to her email, dearmissmanners@gmail.com; or through postal mail to Miss Manners, Universal Uclick, 1130 Walnut St., Kansas City, MO 64106.)

DEAR MISS MANNERS: My husband and I disagree on the subject of what constitutes a house guest overstepping the line when it comes to laundry. His family comes to visit us once a year -- usually for one week -- and he feels it's OK for them to have unlimited laundry privileges.

They will want to do a load about every other day, and always right before leaving, which makes me feel taken advantage of. For the time span of their visit, I feel like one load is plenty -- two would be the max if there was an unexpected problem. Please let us know what is appropriate.

GENTLE READER: You really dislike your in-laws, don't you?

As Miss Manners understands it, they visit once a year for a week, so laundry every second day would be four times a year -- at most. Apparently they do not ask you to do it, but only to use your washing machine.

Small acts of sabotage are unlikely to curb these visits. These are your husband's relatives, and he disapproves of your ploy. It will only make you look petty and inhospitable, to him as well as to them.

DEAR MISS MANNERS: I am a senior citizen who is quite often unseated on public transportation by someone younger and fitter than I am. Yesterday, after I had taken the last seat, I noticed that someone even older and less fit than I was being outraced by a man in his early 20s. I stood up and gave the loser of the race my seat.

So far, so good, as far as my behavior was concerned.

Now the evil part: I was really tempted to say to the young man who had won the race, "If you're disabled, please keep your seat," or "If you're disabled, don't get up. I'll give her my seat."

Later, as I sat there watching him in his oblivion, I wanted to whip out my camera and ask, "Do you mind if I take a picture of you sitting beneath the sign saying, 'The law requires you to make seats available to seniors and persons with disabilities'?"

Once, when I was really tired and traveling with someone 10 years older than I am, I actually told a young couple, "Thanks for saving these seats for us. You can get up now." (They did.)

What can I do to keep myself from behaving in a way that Miss Manners would not approve -- or a way that will get me shot?

GENTLE READER: If you are shot, you may take comfort in knowing that the shooter was behaving worse than you. If, however, you decided that the behavior of others justifies your retaliating in kind, you would be no better.

Worse, Miss Manners would say, because you would be pretending to be correcting the very behavior you are practicing.

But you didn't. You squelched your impulses to be rude and came up with a way of allowing the couple to vacate their seats without being embarrassed. Congratulations.

(Please send your questions to Miss Manners at her website, www.missmanners.com; to her email, dearmissmanners@gmail.com; or through postal mail to Miss Manners, Universal Uclick, 1130 Walnut St., Kansas City, MO 64106.)