About 18 months ago my commute was painful, very painful. My target for a good time would have been under an hour and five mins. I was only doing one way 5-6 days a week.
Now it is not painful at all, apart from occasional Friday legs. My target PB moving time is now 45 minutes. I nearly always work at 70-80% effort, that has become a habit and now and feels natural. The hill I used to walk half way I am now 8th fastest up out of 108 riders on Strava
My HRR has gone from 20 odd BPM at the lights at the top of a high HR climb to 60-70 bpm HRR. I have lost close to 5 stone and all due to treating most of my commutes as a Gym session. At 47 I am pretty proud of that, if you cant tell from this post lol!
For me the key to this was doing miles all through the winter, and not hibernating.