Commuting to/from the shop was key to one of my good years in the 90s. It was 18? miles, a coworker met up with me (usually), and I rode pretty hard. That kind of consistent riding is good. Just make sure you're not reinforcing bad pedaling habits, bad cycling habits. Straight line, good cornering lines (imagine someone to your inside, someone to your outside), smooth one handed riding, etc.

If your commute is less than 20 minutes or so, and you can afford to ride more (i.e. shower or similar at work) then extend the ride. If you can't extend it going in, extend it going out.

When I had a shop, worked 7 days a week, etc, I'd someone regularly do 2-4 hours after work, either on the trainer (indoors at the shop), road (night loop 2 miles all one way or median roads so no oncoming traffic). If I was too tired I didn't ride. Sometimes I'd set out on a ride at 11 PM or later, going for 1-3 hours. I didn't force it though, and if I got on the bike and felt tired, I worked on pedal smoothness and not much else (39x17 or so, spinning 120 rpm avg for an hour, or at least trying to do it).