It would be a good idea to bundle older boss entries together that are a part of the same raid group & instance bosses. This would cut down on the number of entries in the database - allowing for quicker syncs to occur for older entries but might cause an issue with syncing when decay is involved. As long as decay occurs before the boss entries are bundled, it would be effective.

Biggest issue: Entries are uniquely timestamped, so you would have to nullify those timestamped entries, probably using a field called "BundledEntryIDs" or something to that effect that would tell players "This is a bundled Entry, not a singular entry", and what entries to delete from their database.