There are a few commutable lines in each base. I sometimes bid them, but the trip/line construction generally sucks and/or falls over days I don't want to fly.
I elitt so much that it doesn't really matter. I view my line award as a starting point from which to begin working. I bid min days, min block, and try to avoid trips that are going to fall on red days. I rarely fly any of my original award. Plenty of commutable trips in and out of elitt each month if that is what you are looking for.