Mines inconsistent. When I was younger I could not eat any dairy. That was probably until I was about 7. After that, we still limited dairy to a rare occassion. These days I can eat a little at a time (a slice of pizza, chesses on a sandwich, a scoop of icecream, etc.) But I can't eat it everyday or even more than twice a day. Also, antibiotics seems to set my stomach off so while I am on antibiotics and for about a week afterwards, I avoid straight dairy products (meaning, it can be baked into things but I can't have cheese, ice cream, milk, etc). Lactaid does not work for me. It never has. So if my stomach can't handle it, I just avoid it until my stomach recovers.
I still can't stand milk though. Drinking a glass of milk leaves a terrible taste in my mouth and a worse after taste. That is one thing that will probably never change.