How long are you meant to leave the bike (2013 streetglide) warming up before you can take off? 3 degrees C here the other day.

 I start off for work @ 5am mine sits for as long as it takes me to close the garage door, then I just ideal down the road & i've been that for yrs.

There is no real answer for that other than start the bike, put your gear on while it idles and then ride away without reving the crap out of it or lugging the motor for the next 3-4 klm.

The oil pressure guage is a good indication as the oil warms your oil pressure guage should be around 32psi at cruising speed. If it reads higher then the oil is still not warmed enough to "thin out"