All you really need is a large enough rear cog that in combination with the small front cog provides a low enough gear ratio to go up any grade regardless of how steep or how long it is. Whether it takes 10 minutes or 12 minutes to get up a grade is not important. When touring a put a larger cog on the freewheel or cassette and so instead of a 24 x 39 I have a 28 x 39 lowest gear. 4 more teeth may not seem like a big deal but it provides a 16 percent lower low gear and that makes a great deal of difference in the effort/strength required to move the bike up a hill.