I guess I'm in the minority in that I change reso heads a lot for live gigging purposes. You can get by in the studio with basically anything as long as you mic the stuff right and have a giant roll of gaff tape. But, when I was gigging a lot and was playing primarily un-mic'd, I'd probably change all my tom heads after 30 gigs, so, maybe three times a year. I'd change the snare reso the same amount, and the batter probably 4 or 5 times a year. Kick batter heads, I'd basically only change if they got really worn at the beater (I didn't like using a patch). I usually used Fiberskyn kick reso heads, and they seem to last forever. For me and my preferred tuning range (an average, medium tone), the reso head actually seemed more important than the batter head to the overall sound of the drum, so, I put a bit more emphasis on replacing and maintaining them. Almost any drum I've encountered that was 'untunable' had a crappy reso head. Even if you are shooting for a dead, dry sound, a good reso head is still just as vital (if not more so) than the batter for the body and tone. A fresh and proper reso can really help open your sound or, alternatively, focus your sound. It can dry it out, or add pleasing overtones. Chances are that if you find yourself using muffling rings, excessive amounts of tape, moon gels, felt rings, etc is because you've ignored your reso heads. The effect isn't that apparent if you're primarily playing in a garage or a basement or some similar room with sub-optimal acoustics. But once you get that kit into a room that actually sounds good, the difference between a fresh, well tuned reso and an old one can be pretty dramatic. Change your reso heads, yall!