we have a drawing , my parents and siblings and all my moms brothers and sisters and their kids(my cousins), and we draw for who buys for who. And of course each individual family buys for each other however they do.
id say when they can start working for themselves id quit the bigger holidays and more so switch to like life achievements. At the very least when they gradtuate high school that would end the chirstmas and birthday cash. so up until high school graduation i would give cash from like 13-18 yrs old and a nice size gift when they graduate and then just switch over to cards.
my relatives stopped rather young with me, probably around 13-14 yrs old or so.