My problem is that I signed up for daily e-mails showing the latest free books and keep downloading a few more each week. I do read as well, but at the moment download more than I read.
I keep expecting the supply of new free books to dry up, but this does not seem to be happening.
It won't as everyone who considers themselves a potential writer is jumping on the bandwagon hoping that their free book is a hit and it gets them a publishing deal (which has happened for a number of people) or they get enough fans to start charging a small fee.
Also some professional writers are using free books as publicity to increase sales of their other books.
So I doubt it will ever dry up (not to mention new books fall out of copyright every single day)