I've been commuting daily for about three months. My commute is 20 miles round-trip. I'm in southern California, so the weather doesn't get that bad, but most of my commute is on a path along the beach, so my bike gets pretty sandy. I clean the bike and chain every week to remove as much sand/dirt as possible.

I'm wondering how often I should get a tune-up. Some people have said it's only necessary once/year, and others say every few months.