I have just finished migrating my stuff to DN. Numerous backups had accumulated. Just did a Rebuild Database. Can I delete all the backup.x folders? I have faith! Of course, I will do export first.
You could delete them, assuming that you’re backing up your data anyway (e.g. via TimeMachine).
Not using Time Machine. Lion broke my NAS for now. Doing exports for now. Just wanted to clean out stuff that accumulated during migration.
You could also set the desired number of backups via Preferences > Backup. Afterwards use File > Backup & Optimize and all unnecessary backups will be removed.