You should monitor your storage and set up alerts so it won't fill up in the first place.
And its not about the number of snapshots but how old those snapshots are. Snapshots are not for long-term "backup". You should delete them after a few days as they will grow over time. Nothing you delete after the snapshot is taken will be deleted until you destroy that snapshot.
Again, check your TRIM/discard. If you don't set that up properly for every VM and LXC deleted data won't free up disk space even if there are no snapshots.