I began commuting in 81 and continued until I retired for the third time last year. I only live about 3.5 miles from work by the direct route but usually did around 20 round trip unless there was snow and ice. Riding 3.5 in 10 degrees F through the snow etc was plenty. In the summer the mornings were best and the 90+ degree afternoons the worst and the reverse in the winter. You haven't said what you do, but I was in a high stress office job and relied on the ride each way as a stress reducer. It worked well. What you are used to is everything. There were a couple of weeks in January or February when the roads were too bad to ride with single digit highs and walking the trip was really hard work at first. The great thing about riding a bike to work, or walking , is at the end of the day there isn't a lot of choice if you want to go home. I found once I got started I made a few endorphins and was happy as a pig in poo, anyway. Even when it was 100 F if I tanked up on electrolytes and water and took it slower I could get home ok. The other thing is my bikes are all dialed in ergonomically. A bike that is totally comfortable and set up just right can put a smile on your face even when tired and one that doesn't work or fit properly can suck all the joy out of ride in no time. Happy trails!`