How Hot is TOO HOT for the Wolfe Ridge Splitter?

Yes, I had a little fun with the thumbnail. No the splitter didn't catch fire, but looking at the oil temp it got quite hot after just 45 minutes of splitting firewood. This raises the question of what is the appropriate operating temperature for a commercial hydraulic splitter like my Wolfe Ridge Pro 28c? I know if the oil gets too hot, it can damage seals and other internal components, but how hot is too hot?