Braking and especially going downhill is something the specifications address...that too many have no clue of...
If over the ratings...sure the braking system(s) are NOT designed for that and will be over stressed to maybe fail on a long or series of downhills.
The max incline (both uphill and downhill) are buried in the specifications that all OEM's must design to, test to and certify in order to pass
Braking turns kinetic energy into heat and the thermal management system has rejection charactoristics designed in.
By braking HARD to reduce speed below where you want/should be and then allow it to coast (with the transmission in low enough of a gear) will have the thermal rejection stuff cool the brakes enough for the next HARD braking.
Cycle that and you will/should be okay. Repeat that if you are over your ratings...all the components/systems of your TV will be overtaxed and may NOT cool itself enough
and yes, EVERYTHING should be checked and maintained well
Over sized tires (dia larger than OEM), lifts and other after market stuff may affect the performance, so beaware of that