I'm puzzled by the warning against doing consecutive songs in the same key. When you're in the audience, do you really notice what keys the songs are in? Do you really notice when two songs in a row are done in the same key? Have you found that even audience members (like me) who aren't sophisticated enough to be able to tell that two songs are in the same key will sense some kind of sameness and be turned off by consecutive songs in the same key?

[Disclaimer: I never have this problem as a performer, since I can seldom stay in the same key for more than a few bars, let alone two whole songs....]