If I don't have a bunk vent or window open, I'll leave the drivers side door window open an inch or two. I don't like the dry heat either from letting a truck run all night with bunk heat on, so I'll shut the truck off and keep warm with blankets as long as j can.
I'd say from end of Dec to about beginning of March the thing doesn't shut off except for on weekends.
Has it ever snowed that much in Langley BC? I use to live in Burnaby... lasted 2 years. Got sick of BC fast and came running back to Toronto.