I've owned a Heritage and three Fatboys. I've taken the Fatboy on long, long trips. Weeks at a time. I've spent seven-hour days in the saddle and never felt uncomfortable. Wife said she never once felt uncomfortable. Then again, that's with a windshield, Ultimate seats, backrest, etc. When I get home, I ****** all that junk off.

Like the man said above, the Heritage is slightly more comfy. But doesn't look as good as the Fatboy. Here's mine loaded down with some of the traveling stuff.

 

I don't have a Fatboy, but I have a '12 Slim and it is similar enough. I must be different than most. I am 6'2" and 250-280 lbs depending on how much pie I have eaten, and I travel everywhere on my Slim. I have done six SS1000's and a couple BB1500's on it with no problem. It is very routine to leave work Friday night and hit 400 miles before stopping for the night. I think breaking in your seat is key, learning how to move on the bike is important as well. I run many miles with my feet up on the passenger pegs when I need to. I am working on fabbing up some removable whisker style pegs to stretch my legs out forward without having to go full highway bar.

I think more than anything is getting your body accustomed to the miles. I can ride 12 months of the year so I don't have much of a down time and I believe that helps.

 

Never owned a Fatboy but understand your attraction to them. I do have a 16 Heritage and i never feel like I need a break on longer rides other than a fuel stop as needed. Can't imagine the Fatboy would be much different than the Heritage.