I treat the free books like library books. I'll download them if they sound interesting. If they don't hook or grab me within the first chapter or so - it's deleted.
I've got a lot of room on my DR800, so this works fine (just got a big TBR list).
The good thing about the free ones is sometimes you DO find a gem ... and go back for more from the author. I'd hate to miss out on a good story just because I had "too many" free books.
That almost hurt to write: How can you have "too many" books?!
Happy reading!
Marilyn