I've been lucky in thank yous. My niece has always made sure that her 2 boys sent thank you notes. When the oldest one got to be about 16 or so, I told him that as long as he always sent me a thank you note or called, or told me in person, I would continue to give him prezzies - otherwise, they would stop when he turned 18. He just turned 21 & he's still getting gifts! His little brother is just 10, so I figure I'll tell him the same thing in a few more years. :D