I used a 2-wheel burley trailer with front panniers several times, none of which were on tour. I briefly did a mobile bike shop operation where I carried tools and a repair stand in the trailer, and miscellaneous stuff in the panniers. And I also carried most of what I needed for college about 60 miles in the trailer and two panniers. The original plan was trailer + 4 panniers, but I turned out not to need that much space, and using front instead of rear panniers did improve the bike's handling. If you have a good reason for carrying a lot of gear, the trailer+front panniers is a good option.