I generally do it when I find the throttle is jerky when running at high RPM in first. Basically if the bike starts to feel jerky coming in/out of the neighbourhood. You can also do the "snap test", which is just to roll the throttle on when the bike is not running and ensure it snaps back smartly. You don't want any sluggishness in the throttle returning to idle. Check with wheel turned to the left as well.