I don't understand what carb'd has to do with long distant riding. One could argue that elevation has an effect on carbuerators, but you'd have to be pretty damn high up for that to happen. If you ride through the rain, you don't want foam filters (UNI pod filters specifically) as they'll soak up the dampness in the air and clog the carb's, but that's about it.
The longest ride I've been on so far is 240 mi., vibrations was killing my right hand. Changed the grips, and 15t counter sprocket reduced a lot of the vibrations. Also, I recently bought a crampbuster and that even helps a whole lot more.
I prefer the throttle rocker. It's basically the same as the crampbuster, but it's shaped to match your palm better.
I don't trust the ones that mount to the end of your bar and lock the throttle ala cruise control. I knew a guy that loved his, but there's just something about a "locked throttle" on a bike that makes me uneasy.