Commuting this time of year takes a hit -- I go from 5 days a week to about 3 days a week. I try to get a century outside every week, too, but that sometimes falls by the wayside due to weather or lack of riding partners. If the century doesn't happen, I hit the trainer for 7-8 hours (seriously -- I know, I'm nuts) one weekend day. Try to get in a 2-hour session or two on the trainer during the week.
Once the weather starts to cooperate more, commuting becomes a 5-day proposition (9 miles per day), I get in both weekend days (usually a century and a 50-mile ride), and I get 2-3 days during the week after work (30-50 miles at a shot, depending on how much daylight I've got and who I'm riding with). Weekly mileage drops if there's a USCF race on the schedule; increases dramatically if there's a brevet or UMCA event to attend....
Yes, that's a lot of miles. Yes, I have a full-time job. No, I don't do much of anything else.