I feel you on dedicating HD space. I have a 60, and I'm constantly trying to conserve, while my girlfriend has a 300 and stays downloading random shit and forgetting about it. Hell, I even have a few games that I've downloaded onto her console that I only play while I'm over there.

I will say, on conserving space and PS+ "free" games, if you have the room at all, it's worth downloading them and deleting them if you don't have the space. That way, when they're not free anymore, you still have them in your library to download whenever you please.