But I think we are unaware of some problems though faced by using stations for years upon years.

I think one of them is a slime build up within the stations, which renders them useless after a few years, there are prehaps other problems also, (orbit boosting etc) I know very little about this and I would be glad if someone else could enlighten me as to way we can't keep stations in orbit for a long time.

I mean instead of just saying "Alright we're done building, let's de-orbit this hunk of crap and build something else" We might consider just adding more and more modules to it until it's actually a sizeable space laboratory?

If we add a module or two each year it's going to wind up being pretty friggin huge, might not be a bad idea to send up some remote controlled robotic space craft for astronauts to run while they're up there and maybe begin collecting space junk to recycle on board.