I use a lot of different tunings, and spending time with each of them is important. So I tend to swap out the harps I carry with me every month or so, exchanging standard tuning for natural minor, or melody maker, or whatever. This also helps keep my thinking fresh--I really have to focus on what the harp can do, instead of relying on all my favorite tricks.
I also like to swap out different keys, because every key has its own feel. Last month I carried a G harp around most of the time; for the last week or so I've been carrying an F harp. They're way different.
The nice thing about harps, like ice creams, is that they come in different flavors. And once you've learned the basic techniques, you can more or less play them all. Switching to a different flavor helps me to stay excited.
Thanks, Richard Hunter
author, "Jazz Harp" latest mp3s and harmonica blog at http://myspace.com/richardhunterharp more mp3s at http://taxi.com/rhunter Vids at http://www.youtube.com/user/lightninrick Twitter: lightninrick