I'm also one that thinks their's room to be an IBA member & a liesurely destination rider. I do both, having completed 5 Iron Butt rides last year. I do the Iron Butt rides for the challenge, knowing not too riders can ride, e.g., 5,000 miles in 5 days. Believe me, it's harder to do than you might think. Everytime I complete an extreme ride I say that's it. But something brings me back to try another. The IBA proof and documentation standards are very high, making the accomplishment more worthwhile. When I complete one of these rides I say to myself, that wasn't very fun at all, in fact, it was downright brutal. On the other hand, non IBA rides are fun taking your time, viewing scenery, and stopping along the way.
But I know one thing...I'd never put a car tire on my Harley to save a few bucks and squeeze out a few more miles. That's plain stupid, idiotic, and dumb, IMO. Being an IBA rider, EVERY ride requires a fair amount of night riding, and I've swerved more than once to miss objects in the road, some close calls, and I don't want to think what might have happened with a less maneuverable bike. If you want to put a worthwhile modification on your bike for long distance riding, put HID headlights and HID headlamps in your aux buckets. I have, and they have saved my butt many times.