Thank you letters

At work, we're having coffee and comparing notes on Xmas experiences. One young man is whinging about having to send thank you notes to his girlfriend's mother. And somehow starts to complain about his mother. Young man gets little sympathy from the two mothers in the group. And our revered ex-director-of-studies advises him to do whatever his mother says, tells him to use only three words:

"Yes, mother dear!"

And always to use them, varying only to

"Yes, dearest mother!"

Revered ex-DoS says to do what his mother says, always, and be courteous, even though he's also muttering to himself,

"Mother, I'm an adult, I'm over 60 and drawing my pension soon."

My son has sent his thank you letters, and he's not whinged at all.