My editor syncs the total editing state to disk every few minutes, across all open instances.

I eventually added support for killing buffers, but I rarely do (only if there's stuff I need to purge for e.g. liability reasons). After a few years use, I now have 5726 buffers open (just checked).

I guess I should garbage collect this at some point and/or at least migrate it from the structure that gets loaded on every startup (it's client-server, so this only happens on reboot, pretty much), but my RAM has grown many times faster than my open buffers.