Welcome to the forum. As @Keith
says I've done quite a bit to my bike.
For long rides a bat wing fairing is really nice to have. You don't get beat to death by turbulence anywhere near as bad with one on. It's not as much protection as you get on something like a Goldwing but definitely better than nothing.
I never ride two up so I took the pillion seat off and I've put bags and a rear rack on it. V&H exhaust, all kinds of little goodies that you can see in my signature.
Even with all that it's not a great bike for really long rides. The factory seat is no treat and the bike is geared low enough that it's pretty buzzy at 70+ MPH. It'll run 70 all day, it's just that it will tell you about it the whole time. :)
The seat is "fixable" without spending a fortune. I wasn't willing to pay $400 for a Mustang seat so I bought a $70 5/8" thick bare gel pad on ebay and put it under the stock upholstery, over the factory foam. That was about as much gel as could be shoe-horned in there and still get the stock seat cover back on. That is probably the single best upgrade I made to the bike. Road it 175 miles one day last week with no real discomfort.
Another good upgrade is pedals to floorboards - I find being able to move my feet around a little helps a great deal with the comfort.