I'm very proud of the fact that our kids have good manners (except for their age-appropriate amusement at bodily noises at the not so appropriate time of dinner).
Both kids rarely forget a "please" or "thank you", and in most situations they remember to say "excuse me" and wait to be invited to speak rather than interrupting a conversation. (They also use "excuse me" for the bodily noises mentioned above, but tend to follow it up with a hearty laugh, a mischievous giggle, or fake bodily noises so that they can continue to amuse themselves, especially at dinner.)
The one thing the never forget to do, however, is say "bless you" for a sneeze, or "thank you" when they are blessed. In fact, if we forget we are often corrected by our children. And this is what I have come to regret.
Allow me to illustrate with this scenario:
Chris sneezes and I am in another room, so I do not hear it.
Karenna: Bless you.
Jude: Bless you.
Karenna (after waiting for my cue and not hearing me): Mom, Daddy sneezed and you did not say "bless you".
Me: Bless you.
Chris: Thank you.
Karenna: You didn't say "thank you" to all of us. You only said one "thank you".
Chris: That was a blanket "thank you". It covers everyone.
Karenna: No we said "bless you" three times. You have to say "thank you" three times.
Chris: Thank you. Thank you. Thank you.
Karenna: Now you said it four times. That's too many.
Me: Can't someone say "bless you" again?
Karenna: No, we each already said it. We'll just have to make Daddy sneeze again...