I been getting in the habit if I only need to look at it to check it out then undue checkout instead of checking it back in when there been no change.
This is a very interesting question on how they store the previous versions, I Assumed it was a database entry and was there for light weight.
I just so happened to clean out my dev server and reload it with a fresh copy of prod, when I do that I do not bring over all revisions ( If i do it makes the export file huge and takes forever to make and import). I do not need the history for dev so I just leave it off on the export.
Also interested in the answer to this question.