So far I haven't had a problem with burnout, but then I'm not hauling 45 lbs. worth of kid a couple of times a week.

If I had to guess why I haven't burned out yet, I'd say it's because:

1. I plan each week to drive at least once. Some weeks I end up riding every day and some weeks I can't get 4 days worth of riding in. But I usually enjoy my drive when I do take the car. I have a nice commute, both for riding and for driving. Since I plan on driving once each week, I don't feel bad about doing it.

2. I've been really into bikes for the last 3 years. I probably don't go more than a month without changing something. The last two weeks I've been riding without handlebar tape because I've been trying the bars at different angles and adjusting shifter positions. The day I finally decide my bike is fine the way it is may very well be the day I burn out.

3. My commute changes. It might be a change in seasons or just the day to day weather variations. Sometimes I change the route.