[folivier]

Chester is there anyway you can mount a solar panel to the edge of the roof?
Another thought I had was to install a shutoff valve just upstream of the regulator for the bladders and a tee just downstream of that so you could hookup a portable air tank. That way you would eliminate all other sources of leaks and then see how long the air tank would keep the bladders pressured up.
The only problem I see with leaving the batteries on for the 12volt compressor are the other phantom loads. If you could isolate the 12volt compressor then your house batteries might last long enough.
I agree that keeping the bladders inflated would be most important.