Re: Sci-fi series withdrawal
+1 for the Space:Above & beyond reference.
There are also, of course, the Stargate variants. I particularly enjoyed Stargate:Universe.
Farscape was mostly enjoyable - the Peacekeeper Wars washup was certainly worth the effort.
All old stuff, though. Modern ones certainly have a surfeit of teenagers.
Almost forgot : Terminator - The Sarah Connor Chronicles. Yes there are stroppy tenagers in it, but there are also unstoppable killing machines. And Summer Glau.