For most of M2 I've been doing 10-15 questions every day of the Kaplan QBank (both COMLEX and USMLE) random, times. Takes about 45 minutes to an hour depending on how much of it I know.
There's still a lot of stuff (especially stuff in books I haven't gotten to yet) that I don't know but I am using it as a learning tool than as a gauge. When I get done and I notice I got questions wrong from a block I've went through in school I make sure to really pay attention to why I got it wrong (was it that I didn't know the material, did I change my answer) and jot it down in a notebook.