I almost always reboot without the charger, so maybe I'm just lucky that way.
I can tell you that a reboot does NOT take 25% of the battery. I used to do it frequently when I was porting apps (and I was doing that badly ;-). I even have a load-applet option for reboot. It takes some battery, but nowhere near 25%.
(Actually, my battery is getting pretty old, and I suppose it might take more now. I need a new battery. I'm still using the one I got it with, and I have to charge every day now..)

desiv