It should reach 3 bars within a few miles no matter what the ambient temperature. Colder ambient means a bit longer wait. This is a fact. There IS coolant circulating instantly from start. It goes IN the starboard side top of the radiator, and out the starboard side bottom, so not running across the fins, but it will still cool a wee bit with very cold air temps. Enough to make 3 bars take a bit longer to achieve. I ride with temps into the 20's.
When the thermostat opens it dumps hot water in the top of the port side radiator, across the cooling fins and back into the motor from bottom starboard side.
All you REALLY have to know is, if it ever goes from 3 bars to 2 bars, you should fix it. If it take a long time to get to 3 bars, you should fix it.
Or don't. My bike doesn't seem to give a crap how many bars are showing. Runs great all the time. Just fuel economy suffers.
This engine really wants to run at a designed temperature. If the temp is too low it, runs rich until it is up to temp. It's like a punishment for ignoring things. Frankly I think it's far too sensitive and with there was a computer update to fix it.