In the Summer, I try for 4-5 days/wk commuting, regular work week is 6 days. Late Fall, through early Spring, my bike commuting get's pretty sporadic. We still have one car, wife works at home, and public transport would turn my rural 40 min auto commute/1:15 bike commute into a 3 hr public transport epic with a couple miles of walking thrown in for good measure. So I use the car when it is too cold (20 deg F or less), too stormy, or have to do things like pick up my son at his mom's house.