i actually keep finder off (force-quit via activity monitor) until i need it, preferring to use spotlight for simple file finding. it otherwise uses not only too much memory but also too much cpu time (and hence battery).
Also, I'm not sure how much you are saving by doing that. My Finder uses 0% CPU when not being actively used.
dunno why, but my finder uses 2-5% constantly when running, and spawns a bunch of other processes (like mdworker) as well, which also suck away battery. better to keep it off for me.