Ideally I run it everyday on every database I care about. However, that depends on size/resources. I have run it weekly on restored copies of databases because it just took too long and impacted performance. As a result, we had a couple spare servers (old desktops) that we'd added storage to that were dedicated to taking a backup, restoring it, running dbcc, saving results, drop the db, repeat with a new db. In this way, we had a couple systems checking dozens of databases.

I've tended to just run dbcc checkdb by itself.