I don't tour on my Specialized Sequoia, but do a lot of long rides (organized and otherwise) on rural paved roads here in Michigan. It's an aluminum-framed bike and does well at this, but with the stock 25mm road tires it was always buzzy on surfaces like rough chip-seal, not to mention jolting over more prominent surface irregularities. I took a test ride on a carbon-frame bike once and was surprised at how much smoother it was, but I didn't feel I could justify the $$$ at this time.
So this summer I was signed up for a multi-day ride that could include some hard dirt trails and dirt roads, and I wanted to use the Sequoia. I figured that a 32mm tire would fit in the frame and bought a set of Kendas that you might find on a typical hybrid. These tires take only 85psi compared to 100+ in the 25s, and within about a minute of taking my first ride I was amazed at how smooth they were over the rough pavement. It was at least as good a ride as the carbon frame, and made it feel like a whole new bike!
What's even more surprising is that I don't think I've lost anything as far as effort to reach or maintain a speed. In other words, the difference in rolling resistance seems negligible at the most. I do fitness riding with some tri-athlete friends on occasion and my bike does as well free-rolling on the downhills as their specialty bikes.
So the 700x25c wheelset that I took off this summer is still hanging up in the garage. The only other thing that I had to do was to get a different set of brakes since the stock ones wouldn't open wide enough to get the wheels out without deflating the tires. Tektro had just the product I needed.
(I would have posted this in the road forum, but couldn't have taken the abuse I know I'd have gotten. )