I always let the oil circulate fully before taking off, I usually start it and wait 30-45 seconds, maybe up to 2 minutes if I'm not in any hurry. It only takes a few seconds for the header to get hot, I would think the inside of the engine is the same way. but full oil circulation is usually what I'm waiting for, not for operating temps to be reached. It is a complete waste of gas to idle for more than 5 minutes. your engine doesnt get to operating temps by idling in 10 degree weather.
I look at it like this. You wouldnt want someone to rip you out of bed and take you for a 5 mile run, right? You need to stretch, walk around a little, get the blood pumping. I compare my car to a human. give it a minute to get warmed up, then take it out for a run
My boss idles his car for 20 minutes, its such a complete waste, and idling isn't good for your engine overall.