I have been using the same pump for about 6 years now. Initially I had 100' of 3/4" hose which ran about half level and half of it slightly downhill. When I built a storage pad for the camper next to my garage, I buried a 1" HDPE line from the septic tank to right next to the outlet on the camper. That line drops about 2 feet in its 60' run and the pump barely seems to make an effort.
Even when I had 100' of 3/4" I never had any problems with the pump getting hot. I never pumped more than 50 gallons at one time though. Really the duty cycle is more important than how much head the pump has. Unless you were pumping up to an elevation 20' higher than the pump, you should not have any issues at all. If you are worried about it, limit the pump to 3 minutes on with a 5 minute break between cycles. My pump never gets so hot that I can't hold my hand on it and it will definitely take more heat than your hand can stand before you damage the pump. Enjoy your Flojet, it is probably the best purchase I ever made in camping accessories!