Until about five years ago, most of my travel landed me in one place, start to finish. I did loads of backcountry trips with a backpacking pack, but my frontcountry trips were pretty much: get off the plane, go to the location, go back to the airport one week later. For these trips, a rolling carry-on was perfect. But when I started traveling further abroad and incorporating more in-trip transit, I found myself bumping my suitcase down subway steps, back up the steps, along cobblestones, and getting stuck dragging it behind me on less-than-perfect transit days.  Since then, I’ve used a travel backpack for all but my simplest trips. I travel up to a dozen times a year with a travel backpack, including three weeks in Japan with REI’s Ruckpack 40 and 23 days in Thailand and South Korea with the new Cotopaxi Allpa 50 .…