That sounds more awesome to me than anything else. I love multi day rides by motorcycle! I always try to plan my ride around 200-300 miles at a time (and really try to stay towards the bottom end of that number) and it had always treated me right. If and when I've exceeded that 300 mile marker, it always starts to ware on me, and the riding isn't fun anymore. The only times it has been fun to ride any more than that would be when I'm with a larger crew of riders, where the exhilaration of riding with friends out weighs the wear on my body.
It could be good to consider ergo's on your bike if you are getting that beat up - have someone take a picture of you on your bike and look at the alignment of your back, look at the position of your shoulders, look at the shape of your arms. You should have square shoulders, your back should be straight, with your rotation at your hips, and you should have a slight bend at your elbow. If you have a curved back, try sitting further back on the bike or moving your bars forward or up or both. If you drop your shoulders forward, then make the reach shorter, or sit more forward on the seat. If you rotate your shoulders back, (also perceived as dropping your head/neck forward), then try moving bars lower and more forward. If your arms are locked out move more forward on the seat, or move the bars up or back. If your elbows are bent past 45, then lower your bars or move them forward. These sorts of adjustments will make a big difference in how you feel at the end of the ride, and try your best to adhere to good posture, as described above. The goal is square shoulders, neck straight off your back, slightly bend elbows, and a flat back rotated at the hips.
Stretch before riding! Seriously. It will make a big difference. Especially your hams, back, shoulders. Neck, abs/core and calves/quads. You might feel like a dirty hippy doing yoga in your leathers, but you'll look way cooler when you get off your bike without monkey butt!
Finally, it's always worth thinking of what people were doing just 200 years ago to cover the same distance. Poor ass folks like most of us travelled by foot, or by box car. Count your monkey butt as a blessing in disguise.