My boiler has the 90- 110 version of this switch in the upper smoke chamber - I monitor that.
Under HARD burn I see surface temperatures exceeding 375 - occasional spikes 10% more -- the switch lasts fine in that environment.
But I will report that early on --- to fool it and get fuel to a new fire --- I would hit it with my propane torch so it would see 110 a bit sooner
-- once I hit it too hard and it didn't like that.
Grainger had me a new one the next day