The other thing on a tour is that you are traveling over roads you're not familiar with. Instead of subconsciously remembering where the bumps are on your normal commuting or training local rides and avoiding or mitigating most of them, you end up whacking the wheel against the potholes more. This is especially when you're tired and hurting after a long day in the saddle and the traffic is heavy which limits your evasive action as you come into the town you're staying in that night. The roads in towns tend to have more rotten pavement than out in the country because, unlike us, cars and trucks go more slowly in towns so their tolerance for battered pavement is higher. Get a 36-hole rear wheel, even a 40 if you are a big rider or carrying full camping gear. 36-hole always worked for me but I liked 40 when we did unsupported non-camping touring on the tandem.