Temperature is more important during primary fermentation. During aging, especially for traditional meads, you can keep them stored at 75-78F and they'll do okay. Perhaps they won't survive as well as they would if stored at cellar temps, but they'll be good for several years at a minimum (perhaps a lot longer). With some melomels, that may not be the case.
As for 71B, some folks have found it to work OK in the upper 70s. I prefer K1V or D21 at that level, but I'm planning some more testing with 71B.