Log table can fill up quite a bit, so it would be nice if it would clean up automatically. Multiple ways of doing this but the most logical seems to be to remove everything older than X days (configurable). A similar approach already exists for cache cleanup which simply the "next clean up time" and checks every time whether it's passed it and if so removes everything older than X.

The downside of this is that (currently) it uses the session to maintain the "next clean up time" which means every users triggers the cleanup rather than just 1 (same applies to cache clean up!). One way around this is to store the time in the database (i.e. a global session) and do the check based on that.