I've noticed that for docs with 10K+ versions (40 edits per day), it starts to lag, delete info, kick me out of editing, etc. Some suggestions:

* Instead of creating a version every time I leave the document, create a version every 2 hours or so.

* Delete old versions after 3 months.

* Lazy loading for old versions

* Give the user the option to modify these parameters, for special edge cases.