I use Chevy ULV 1.2ghz running 1.2ghz on demand. I typically get 8-10 hours of normal use before I hit 40-50% left. I never have had any stability or heat issues and it registers around 1600 quadrant score.
ULV made my phone bootloop, I was using a Chevy ULV 1.25, then moved to the LV 1.25, dont use my phone much during the day, service is meh, but from 9am-10pm I can get to about 60% battery without issue
I use Chevy ulv 1000 I don't keep mine above 800 unless i need to get some more out of phone. And my low is 400. U should Max it out like u said just to see what it can handle at Max but really there should be no need to go over 900 (1000 for streaming purposes).
Since all phones are different, you just have to experiment to find the right kernel for your phone. I run Chevy's ulv 1.25GHz kernel and have it clocked to between 1000/250 - 800/250 (awake); 400/250 (screen off and charging); and 250/250 (above 114°). I also have my sampling rate set at -1, WiFi, Bluetooth, and all locations turned off. My phone is EXTREMELY smooth, responsive, and FAST! My temp never even hits 100°. On a light usage day, I get about 20 hours one a charge. On more moderate to heavy days, I usually get around 12-16 hours...give or take.
Btw, anything that is an "auto kill" (assuming its for task management), should be uninstalled. The OS manages tasks on its own and task killers with auto kill turned on will only hurt your battery life. I DO use Advanced Task Killer for Froyo but only the widget..auto kill is disabled.
My droid can't handle the ulv kernels but it seems to be working fine with the lv 800 mhz. I'll keep this for a while and see how it goes but so far its been going great(performance wise). Battery life's yet to be seen.