You are right, Mark, that Cessna was THE plane to actually really ask for that feature.
The default FSX battery life is modelled way to short, so the only workaround for e. g. entering the plan and setting up the G1000 in general is to have a FSUIPC battery or to start the engines, which, in my eyes, would be a total loss of rw feeling.

Maybe, because we have that option enabled, the CS 727 also profits from it. I never tried running FSX without the FSUIPC battery since then.