Wouldn't a person think there would be a hell of an uproar if a particular brand of battery maintenance device tended to fail.
Key words...
Possible
Likely
It's "possible" to win a billion dollar lottery. But "likely" isn't in the scenario.
Kalispell, isn't banana-growing country. Minus forty, would not make the newspaper in London.
For the cost of a battery maintenance product and total aggregate kWh consumed during a season it's a tough job arguing against using a battery maintenance product.
Make a 10-gauge jumper clip to short the house battery with the chassis battery and that way everything stays topped-off.
By fully charging both batteries, connecting them together then verifying with a volt meter a week later that battery voltage is being maintained (no sneak draws) confidence can be gained that the system will survive a winter just fine.
As a side note, I was not aware of any gasoline engine ECU that had a 0 milliamp draw when left connected. Do I need to update my opinion?