Unexpected mileage

I've been pretty good with alternating my bike/run every other day so my knees don't revolt on me. Now, however, with the wife's car in the shop I get to commute to work on said bike. It's an easy 20-25 minute ride(depending on my effort), so I'll get to increase ride time for the next few days. This also works well to flush the system of any previous harder efforts in the day, ride or run. That's if I can manage to just "casually" ride to/from work.