I know people tour on just about anything. Really, for me, whatever I settle on for my commute tends to end up as my touring tire as well. I started with 700 x 32. Tried to go thinner with 28s. Decided that was less comfortable, so I went back to 32s. Then 35s. Then I ended up on Vittoria Randonneur hypers in 38/40 (depending on where you take the measurement from). At that point, I couldn't go any wider without replacing my fenders. Never had a desire to go narrower. Instead I replaced my bike, which now has 26 x 2.15" Big Bens. Daily commuting, plus it's been on some long, weekend bike-camping trips. They're great for pavement, and they don't mind dry hardpack, either. I'm hoping to bike the GAP & C&O this year, and I wouldn't hesitate to use the Big Bens on that that trip, from everything I've read, but I'm also building up a "26 plus" wheelset, and I'm considering using Surly Extraterrestrial 26 x 2.5" tires for the trip. I guess if I keep on this way, in a few years I'll be riding a fat bike with 5" tires everywhere.