I have slightly over 10km one way commute. I have a bad habit of getting very fat in the winter. I still commute most of the winter but it's only 28-35mins each way in winter conditions. It's about the only exercise I get in winter.

In spring I also start to "train." So I do "real" rides in the evenings and weekends in addition to my commute. I don't count my commute in my weekly training hours since it's such a short ride. I do 10-14 hours of "training" a week above and beyond my commute. The snow here is all gone and in my current condition my commute is now taking 22-25mins.

By mid-summer I will get that time down to 17-18mins for 10kms. One of my goals this summer is to do it in the low 16min range. Right now it's a challenge to average 25-28kph at a tempo pace, by mid-summer I can average 35-38kph at a tempo pace.