"Drain the battery, can't start the engine, still stuck, no more heater..."

That's basically where you would be if you didn't use the heater, and croaked due to hypothermia, right? They would tow you out, anyway.

Trying to get the last six starts out of old or defective batteries in winter is just begging for trouble, anyway. There's no point in waiting to where someone's life or well-being could be in danger.

But it would be an interesting experiment for someone who knows about that stuff. If it's really do-able, it would ease the mind of people: "It's okay, Honey! If you get stuck with the kids, just set the heater on full blast and turn the engine on for a minute or so every five or six minutes, it won't hurt anything."

Ignorance isn't bliss, it's scary in a survival situation.

Sue