It keeps 30 days for free accounts. That's unlimited for Pro IIRC (although you have to manage according to free space)

Edit: apparently policy changed at some point and versioning does not count in your quota. Also, Pro accounts need the Pack-Rat extra to enable unlimited versioning.

I wish I found out about this within 30 days of my file getting corrupted. Strangely enough I posted my issue on the Dropbox forums and a Dropbox admin didn't mention this, he just said it's a problem on Keepass' end.

I use dropbox on multiple computers. one of the computers is running jungledisk to backup whole dropbox content. The problem is both services work on top of amazon cloud but I will eventually resolve this issue too.