One thing you want to keep in mind is that the always hot memory-power has ZERO draw as far as running the battery down. Mine can go many months and it has zero affect on battery drain. And I will bet big money that there isn't a car on this message board that has a system, and its related components, that have the amperage draw as my mega-suck electrical demand than the system I have in my car. The picture I posted at the fold down rear seat is merely the tip of the iceberg, one dinky component.

If the memory drains your battery, you have something hooked up incorrectly. Myself, I would rather put forth the effort to fix whatever is wrong rahter than jury rig around it.