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

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.