This question came up the other day:

What sort of performance hit is caused by having pages with many revisions (for that matter, what would be considered a large # of revisions for SilverStripe pages)?

Some of our pages have perhaps 150 revisions on sites with 500-2000 pages. Some pages are short, some are manuals/documentation that can be fairly long with many sections.

We're trying to determine whether to start purging the oldest pages and what a useful threshold (time / # of revisions) is useful to keep around if there is a serious hit on performance.

Anyone investigate something like this?

For the general performance, lots of versions shouldn't cause any performance issues as I don't think anything will query your versions table. You can check the MYSQL queries that get executed on the page and check if any of them query _versions.