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’s 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.

New Miss Manners columns are posted Sundays, Tuesdays and Thursdays on www.washingtonpost.com/advice. You can send questions to Miss Manners at her Web site, www.missmanners.com.

, by Judith Martin