I am up to 3700 yards per practice now. I'm getting a bit tired! I did about 200 warm up, then I did that Janet Evans ladder again, 1X500, 2X400, 3X300, 4X200, 5X100. Easy to keep track of yardage and gets it done. Took 1 hour 15 min. I rested about .30 to 1:00 between sets. Yes I know Janet did shorter intervals! I'm getting some sensation in my lats, maybe I need to stretch more.
I'd heard that as masters swimmers age up (also runners, bikers, etc) we are able to do endurance type stuff better than sprinting. I'm finding that to be true, whether it is because of slow vs fast twitch muscles or mental toughness. I'm more concerned with finishing than being fast- the old tortoise thing.