Changing it from 2 to 1 on my mogul definitely made a difference, and the added drain was negligible. I haven't changed it yet on my TP2 yet 'cause no one's complained, I'd forgotten to, and I was already having batt issues.
The battery issues went away when I uninstalled the nueBattery utility that shows battery remaining in 1% increments. My idle usage dropped from the 170's to 50-60. (maybe I had an earlier version, haven't checked yet.)
AFAIK, the slot cycle isn't reset by anything OTA from the tower, but from a WM process running in the background. I can't see recall what it is looking at my process list, maybe HTCGuardian? I'm guessing it was disabled by the cleanup cab.
I'll likely change mine shortly now. You'll need your MSL to change it. Unless you're on the fringes of a tower (therefor needing extra power to reach it) the extra drain shouldn't amount to much. YMMV.