what I don't get, are the guys who can do double centuries. talk about hours in the saddle ...!
for me two hours in the saddle is pretty satisfactory, but I did do one all~day ride last fall. finding the right saddle for your butt is certainly a consideration. my road bike has a classic Brooks & my mountain bike has an inexpensive spongy "ergonomic" saddle. I don't use "padded" shorts, I prefer thin lined, tri-shorts
good luck with your personal quest!