Depends on the car... my current pride and joy (v8 commodore - until I get enuf ca$h together for the R33) gets started, left until the revs settle in (usually about as long as it takes to kick on the CD, get my sunnies, light a smoke and roll down the window). Then gets taken easy until the needle moves towards the H and settles between 1/4 and 1/2.
I don't see the point in idling for a long while - seen what it does to diesel generators (glazed bores = bad ), imagine it wouldn't be any better for a petrol one.
The beater (read for the train station) gets kicked over, dropped into gear and gone str8 away - but for $300... who cares anyway , come to think of it.. not even sure if the engine in that even needs oil