I am in the belief that free books don't count in your TBR. Consider them library books that never expire.
I am having some difficulty resisting the Mickey Spillane special on audiobooks at Downpour this weekend. I would not get to it in like 3 years. By then, it might be on special again. Or, I might want to read something else and it would become a permanent member of my TBR.
But it's on sale!