I try to practice everyday - meaning I'll run the sets of my regular band (iPod playlists) or work on my walking or right hand technique, but actual rehearsal (playing with the band) happens once a month or less.
We all live in different parts of the country (Leicestershire, Lancashire, Manchester and the Fylde coast), so all getting together to rehearse is a bit of a logistical nightmare. On the plus side though, everyone does their homework, and we plug in and we're pretty much gig-ready in an hour or two.