At the speed and capacity were running the auger I doubt heat or torque is gonna be an issue, been doing it a long time without much issue other than an occassional shear bolt.

Only running 1000-1500 bph through an 8" auger thats running ~ half speed.

Between filling bins during harvest and moving corn for grinding purposes during the year our augers do a lot of continous running.   Only time we've ever had a gearbox issue I'm pretty sure was do to lack of lube and that was many years ago.