I always try to conserve my machinery:less wear and tear on the bike,less wheel spin,less gas burned and less fatigue on my part.Your KDX is a torquey machine and I would take advantage of that (more traction/less wheelspin) and ride it in the meat of the powerband and not rev the guts out of it.
Often the final 15 minutes of a ride is the most intense,everybody thinks they are in a last chance qualifier as they try to get back to the trucks first.