When does one stop being the "baby" of the family?

[Clodfobble]

I think about the only thing you can hope to do is redirect their efforts. Make it as clear as you can what things you do want--even if that "stuff" is actually stuff that someone else you know or the charity you work for really needs. Electronics could go to the children's ward of a hospital, food could go to homeless shelters... If you really want to drive the message home, forward any thank-you letters you get.