[Users] usrloc, presence etc. cleanup rate: OpenSER mysql backend

Hello, I would like to know how frequently OpenSER are cleaning up stale records with the mysql backend of various modules? For instance, active_watchers, location, presentity, watchers etc. mysql tables, or are stale records automatically removed at all? As I found a row in the location table with an "expires" date more than a month ago, but was still not cleaned up today. Or OpenSER takes a different strategy? This is because we expect to deploy OpenSER on a fairly large network and we are estimating database size and related overhead, and we are a bit worry that accumulation of these stale records may increase our processing costs. Thank you in advance for any insights. Regards, Bernard Chan.