I'm undecided about that. On the one hand, deleting events from the DB that are more than 90 days old would definitely stop the DB from growing too quickly. On the other hand, there needs to be somewhere that all these notes are preserved in perpetuity so that they don't disappear. I've received about $120 worth of Bitcoin to my donation address in my relay description, so if the donations keep coming in I'll just keep expanding the storage space. It costs $10/100GB/month for storage and an additional $40ish for the server itself.