I have a G23 and if I'm not playing it, it's turned off. They draw about 245 watts of power. In 24 hours that's 5880 watts or 5.88KW/day. In a month that comes out to 176.4KW (5.88KW X 30 Days). At my ridiculously high energy rates here in Michigan (I hate Consumer's Energy with a big purple passion) that would come out to $31.75/mo in energy costs for just the G23. No thanks. Not to mention the wear on power supplies, the monitors, fans, etc. Just turn it off if you're not using it.
G23's do have TellTale batteries that need to be charged or you will get an error message, so turn it on once a month or so for a couple of hours to keep it charged. Wish I could find out a way to bypass the Telltale battery circuitry, but IGT hasn't released schematic diagrams for the Blackfin board, so modifying it to bypass the battery requirement would be difficult. It is a good idea to remove them from the Blackfin board to the bottom of the cabinet where they won't damage a board if they do start leaking...which they will eventually if neglected too long.