It is simply unfeasible to remain at the controls
Is it also infeasible to shut down to perform the loading, fueling etc? I can imagine that in a few circumstances, shutting down may not be a good idea, but I have yet to encounter these circumstances. I note that you finally allow for that, but am wondering why one generally would not do so? I have heard the argument about "saving cycles" ad nauseum. Cycles are part and parcel of turbine helicopters, and to those whose only rationale is saving cycles, I say "get over it!" Similar view on saving time except in really unusual ops - combat, paramilitary, etc where the participants are highly trained. By not shutting down, one is making a tradeoff to accept increased risk for some other perceived benefit. Might work out, might not. There is an NTSB accident report involving a B407 in which the pilot exited with the engine running to accomplish something (I dont recall) and then walked back into the MR blades. The PILOT for God's sake! He now has an eternity to consider how much the time saved was worth. !!!! can happen to anyone.