I had an RDL on a previous bike and it was a game-changer. I could sit on that seat all day, every day, with no problems.
I promptly ordered one for my ST when new and I found myself sliding forward. I sent it back for alterations and I still couldn't get comfortable on it.
I sold it and bought a Sargent, which causes me to squirm around after a few hours. I notice the welting at the seam was rubbing on me and seems to be the source of most of the discomfort.
My next move would be Corbin, but I might be leaving the fold entirely this Spring.
I've put more miles on the stock seat than any other., and if I had to choose a "most comfortable for long hours," the stocker would probably be my pick. Perfect - no. Best so far - maybe/ probably.
Unfortunately with seats, the only thing for it is to buy one and ride a bunch of miles on it. You won't know if it'll work for YOU by talking to others, or sitting on it for 5 minutes in a showroom or at a rally. It's one of the biggest bummers of motorcycledom, IMO.