How do you celebrate your sims' birthdays?

I generally play legacy style, so for toddler>child and child>teen I'll throw a party and invite over friends and extended family. But then I don't use the cake to age up, but a cheat. I've got a perfectly good plate of Perfect Vegetarian Grilled Salmon right over there, don't you dare fill up on cake!! Baby>toddler is usually a cake with just the household. Teen>YA is usually a party at home with their friends (and future spouse), so I can make them age up as well via cheats. Also I'll have to spend some time in MC:Stylist to make sure everybody has presentable clothes.

YA>Adult, or Adult>Elder, they generally just age up on their own.

it depends on how much i like the sim if i like them a lot ill put on a big party at my house and if i dont ill just age them up xD

I usually miss their birthdays, but lately I've been at least baking cakes for them to avoid the negative moodlet. I think the birthday parties would be fun if I threw them, so maybe I'll start.

It depends. Sometimes I throw parties,sometimes I just ignore the birthday and let them age up.