I'm thinking you'll need to fill it all the way so the silicone doesn't yellow, crack, dry rot, etc.
If if was me (which it isn't, obviously, but it was when I gave my full setup away) I'd get rid of the tank or keep it, but I wouldn't bother trying to hold onto it if it's going to be four or five years until you're using it again. Keep whatever equipment you'll need for down the road to help defray the costs of starting back up when you get ready or for using in your next smaller tank, though.
I'm picturing a tank chilling in the garage for that long getting pretty darn nasty, and there's always people that are in your exact shoes getting rid of their similarly sized tanks. Perhaps you know where you'll be when you graduate, but I think it'd be easier to settle somewhere and then find a good large tank there. Good luck with college, btw.
Sam
Just read that you still have a year--do a low-tech setup and enjoy the large tank since you got it.