First(an associative list, which makes much more sense in my opinion, even if it's with only one element) :
mob/var/list/Age = list( AGE = AGE_TIMER )
// AGE would be a number and AGE_TIMER would be the value\
of time for the next incremention on AGE
Secondly, two vars..
mob/var
Age
Age_timer
I would use the first one, but I'm not sure how much of a disadvantage it's in (if it's actually in one) compared to the two vars.
I actually have some other stuff I want to implement which go with the same basis as this, so I'd really like to hear an answer on this.
Thanks :)
I think instead you might want to start wondering which would fit best for it's purpouse and would be easiest to handle/manipulate in the future.