I agree with Gixxbynite, a lot of your endurance comes from your desire. That being said, The ergos on an R-1 ARE rougher than the FJR.
I do quite a few road trips on my r-1, one of the most recent was 2520 miles in 5 days, it was an awesome trip, we started in Utah went through Idaho, Oregon, up PCH to Washington, and back through Idaho, Wyoming, then home...
I have Giles Tooling 60mm risers and Variobars, which helps a lot, but I'll tell ya the old butt is feeling the pain if the 500 mile day consisted of 55mph back roads.
Now I know this is a Yamaha forum and I hope I don't get banned for this
, but my dad a long time sport bike rider and road triped a ZX-11 from age 35-42, then a ZX-12 from 42-49, and now he rides the new Concourse. I've spent quite a bit of time on it and I am impressed. If you are looking for a bike that can cover the miles comfortably, has detachable hardbags, and is fun in the twistes, you should take a look at it. That bike is no joke.
Long story short the the ability to ride an R-1 far depends on your desire, your fitness level and how creative you can get with body positioning to distribute the weight differently