I was only in for 11 years and I had a very hard time getting back into the swing of remembering everyone's birthdays. I'm late on another one, as a matter of fact. Back when I was fully immersed in dubdom I used to go to work on my birthday and not even remember it.
You would think because I wasn't raised in the religion it would be easy to go back to celebrating, but it really was very difficult for the first year.