The 'unloading' is due to two velocities of the prop. There is the basic rotational velocity and we get that on the ground. Then, there is the velocity of a volume of air going through the prop disk in flight and is added to the rotational velocity. The formula uses a lowercase v and uppercase V for these, so you can plug in numbers like Pe did for his calculations. Tarcure is measuring this accurately and his numbers hit right in the range that SrTelemaster150 suggested about a week ago as a rule of thumb. I don't think that discussion was in this thread. To be safe, it is a good rule to allow no less than 1000 rpm for 'unloading', but don't be surprised if it starts approaching 1500 rpm when onboard telemetry is used.
Turbines probably don't need much heat protection when it comes to lubricants. Not the ones I was around some 20 years ago. The only heat problem area on one was the bottom of the combustion liner where hot oil could pool up and goo up the area on shutdown. The front bearings of a small Allison turbine would get too cold and engine oil was routed through the stator vanes to heat up the #1 bearings. The hot end of the engine where either TOT or EGT was measured was basically just the tail pipe, and no lubricant on earth would stand up to those temps. Max TOT was 927 C for 9 seconds during startup on the Allison. The synthetic turbine oil thing was a bit of an expensive venture, imo. The real heat in a turbine is only in one area and is blown out quickly.