It seems like they forget about them once they add them. Have you ever considered micro payment model? 

Such as charging extra for long-term storage or offering an additional fee for allowing users to migrate all their data at once or auto backups? 

I think people will pay for these things, it will also create good user and relay relation. I mean you are literally the engines. 

 Good ideas. We considered the export but your tool works well. As of now we have not pruned the DBs. Understand why people are trying revenue streams since donations have dried up since the Apple/Damus drama.