Noticing how much trouble migration caused here lately I have one or two thoughts.
Is there anyway the database can be cleared...of dead/closed/unused threads periodically,so there's more space?
Maybe have a sticky here where users can ask for a particular thread on an active Forum to be closed/deleted(because its no longer needed)? Perhaps make a rule where if a thread hasn't been posted in for 6 months or more,then there can be an option to close or delete it?
Just thinking out loud