I use special home-brewed, boutique batteries. They last a l'il bit longer, and they are kind of expensive, but wow.. the sound is transparent...
I avoid batteries in my effects, as they seem to suck down batteries faster than I can replace them. I looked into NiMH, and NiCAD, the problem is the 9volts aren't true 9 volt. They actually max out at about 8.5 volts, which means they last about 3 hours of actual use, before the voltage drops low enough that they need replacement.
I've been using Energizer Titaniums in my active Pre-amps.