20 years ago I could do 2 RT's a week of 54-57 miles each RT.

Can't do that now, got older and it's really tiring if I'm group riding on the weekend as well as swimming.

I still love commuting but will (and can safely) leave my car (and spare clothes) at work, ride home, then ride back in the AM. Or I'll park and ride, cutting the RT down to 38, which is more manageable. I thus do a short RT as well as one ride in/ride back, per week for 96 miles or so. I also will not commute after dark and stop in late October.

I too do a mix of back streets, bike lanes and paths, along with 4 miles or paved boardwalk on the south Queens, NY beach. In the full distance home and because I do so many side streets I make something like 30 turns on a convoluted route, all to avoid main routes and traffic. I've discovered all those turns, plus the accelerating back to speed, is very tiring, this found a way to park and ride.

EDIT: And yes, I think 50 RT is out of normal with 30 RT or less being more typical. Spending 2 hrs. on the commute on the end of a work day gets me home 6:30 - 7 ish and is late enough to make me have to hustle to get anything else done after dinner. I'd love it if my job were 12-15 miles away, but I do get some good rides in !