chainsaw cylinder temperature?

I've been using my late 90's Husqvarna 350 to cut slabs from a large log, to fit it into my sawmill. It's a high end homeowner saw, not for commercial use, and I already damaged the plastic housing by running flat out too long on a 90+ day. I've been idling  and then stopping when the cylinder fins exceed 350F on an IR thermometer. Does that sound reasonable, too much or too cautious?