I have an MSI Ventus RTX 5090. It gets to 70C GPU temp and 76C on the memory temp (as recorded by GPU-Z) when running AI workflows in ComfyUI. I have all case fans running at 80% to vent the case including an extra upside down fan placed on top of the GPU open heatsink to help pull air through. I am running MSI afterburner at 70% power limit to reduce power draw at the wall maxxing at 620 watts on my 850W PSU. I am using FanControl v226 to manage fans and have set various profiles based on GPU temps. The one thing I CANNOT get to work is forcing the GPU fans to run at aspeed I want. It simply wont do it and insists on running at 30% most of the time, but I would prefer it set at 50% fixed to preserve the life of the GPU. I am satisfied with 70 - 80C but not higher. Long periods of 80-90C on the memory might fatigue it and reduce the lifetime, but I'm no expert.
What temps are you getting during your workloads ? 1000W+ is a lot of heat to expel.