I live in the country where I have the luxury of lots of interesting roads without much traffic. 90% of the time, I start over the same 3.8 miles: left out of my driveway, a nice 70-foot climb to warm up, a thrilling descent to the river valley, then a few miles north through flat, fertile river bottom land.

After that, options: north on the flat terrain, east toward gentle, then increasingly insistent hills, and variations combining elements of both. For days when I don't have much time, I have a few 14-18 mile options, depending on whether I want to climb or not. When I have more than an hour, the options multiply. I'd get awfully bored around here if I did the same loop all the time.

However, when I lived in a city, I found myself doing a number of fairly similar, if not identical, rides, because there was one nice route to get to the woods as quickly as possible, and then a limited number of options in those woods (Paris and the Bois de Vincennes).

If you track your rides with a GPS or smartphone and then upload them to Strava or another site like that, you can compare performance on segments of the ride, even if the total ride is different.