Depends a lot on climate. Here in Sask, Canada, temps of -30c are not uncommon. My new Massey 1742 cab tractor doesn't get put to work till I get warm air from the heat vents. Usually about ten to fifteen minutes. A couple of minutes after initial start, I bump the idle up a few hundred to aid in the warm up. In warmer climates I'd still warm it up for five minutes or so. Doubt there are many things that need doing on a moments notice. Of course there are always exceptions. I have a Scan Gauge in my current truck, gives temp by the numbers, truck doesn't move till it hits 125 f, then operate a tad slow till 150-160. The rise to normal is quick after that. Lots of info out there about warm up time, many say not needed, but they're not footing the bill when a cylinder gets scored, resulting in lost compression and oil consumption.