(See also M*A*S*H, an 11-year series about a 3-year war.)
I think Smallville is almost as bad as far as time-warping, if not worse because the characters are supposed to look like kids, not 30-somethings.
That's a different issue. The events of the series were indeed claimed to span ten years. Regardless of the actors' ages, Clark was supposed to be in his mid-teens when the series started and his mid-twenties when it ended. So that's not time compression or inconsistency, just Dawson Casting