I think 2 years is too much; north Korea or not. Besides, most of the guys aren't actually doing the 'hard' military stuff. A friend of mine was more doing like civil services within the army. Heh, and I know that the guys from Crying Nut were in the music department of the military. So it's not like they do nothing but learning to defend their country for whole 2 years.
Damn, and Heechul's one of my favourites there and now he's gone for 2 long years...