The air pocket thing seems to make sense. Excellent advice to unplug when you start it up... then you won't forget and end up dragging it with you to work.

I've found that in any weather as cold as -10C or 14F, 4 hours of plugging in works good. It was -49C or -56F in the wind here last week. As soon as I got home from work, plugged in and did not unplug until I started up to go to work the next morning.

I have backed out of the lane with it plugged in once... the snap of the cord made me cringe.

 

I have plugged into a timer that comes on two hours before I plan to leave, and I unplug it as I walk by before I get in to start it.