Many many years ago in my forties, I rented a new Sportster one afternoon from Quaid in SoCal. In the 24 hour rental time , I put on 1,400 + miles.
Never even heard of the Saddlesore thing. I just wanted to ride. With that little peanut tank, it was easy to stop for gas quite often to stand a stretch for a bit. And then ride some more. I got home late in the evening and slept for a few hours, got up and rode some more till I ended up back at the HD dealer to turn it in and get my deposit back. Back then it was $125/day plus gas/food. I didn't keep track of the gas/food cost, cuz it didn't matter to me. Loved to ride.
And by new, it had a little over 500 miles on it. I asked the service guy if anymore easy break in time was necessary and he said that, "we break them in as we like to ride them". If you ride at 80 mph, your good to go.