I'm sure it's safe to delete most of them.I just keep my two previous backups here.It would be nice if Adobe could add an option to automatically delete older backups (user configurable of course) to save HDD space.
I use Hzel to do that. Watch the backup folder and remove elements older than xx days/weeks.We're on XXI century… don't waste precious time!
What is Hzel? Also, what is the backup folder (I'm using Windows 7)?
...i simply include my /lightroom dire, which has the cat, prefs and settings, in my normal backup routine.