how old are they?

I always thought that the s.p.d.-ers had passed the general high-school adolescent age that this show seems to base its characters on. Perhaps it was because of the fact that they were police officers, or maybe they looked older to me (I realize that actors can be a LOT older than the characters they play, but...) or the fact that they made a reference to being "old" in the episode "Sam". Teenagers don't talk about being old, do they? I happily remained with this theory until i watched "S.W.A.T." where they're all bickeringh and Cat mentions that its normal for teenagers or something to that affect... i was in shock... what gives? umm does anyone know how old in general they're supposed to be?