Although it is not necessary, I always do a step mash with my Helles, a Beta rest at 149 degrees F for 15 minutes, ramp the temperature up to 156 degrees and do an Alpha rest for 30 minutes, then ramp up the temp to 168 degrees for a mash out With the ramp times during the step mash rests, the total mash time is an hour.
I have done both a single infusion and a step mash on this beer and seem to prefer the body and flavor more with a step mash, YMMV.