Typically the coach making the offer will give you some kind of an idea. If not, it's ok to ask. A lot depends on the kid and the offer. If it's a stud that they know they want, they may make a better offer....but give you a short period to accept/decline....trying to "force" you to make the decision. I don't know that anyone can give you a "typical" timeline on how long it's good....there are just too many variables