My commute is 16 miles each way. Honestly I like this distance. It is long enough to get a good workout (I don't run or do any other exercise on days I ride) and this is a long enough ride to warrant the effort of putting on all my bike clothing and showering. I think the best commute is either under 3 miles (wear street clothes) or over 15. Unfortunately my life is pretty hectic and I'm lucky if I can ride in 3 days a week. Maybe not riding every day is the best option for you too?

-Scott