How long after starting do you wait to click on the high idle?

Mine has 2 speeds only, fast and faster (1200/1700)
I cant see that 1700 no load rpm can be good on a cold engine.

Should i give it a minute or two to circulate the oil and then give it the 1200 rpm speed?

I usually give it a few minutes (2-3) before bumping it up to 1200. I only use the 1800 when winching or when my inverter is drawing a heavy load.