I just don't really see what's so special about it... in fact, the last one I really celebrated was my 15th, since then I just didn't care about them anymore, it's just a number changing from one state to another really
Since I met furs I use my hatchdays as an excuse to invite them to my place to have a party. I don't feel special about the age (my species has a different attitude towards time anyway), but it has proven quite effective to lure furs into my lair :)
* wonder whats inside >=3*
*offers cake*