I'm into a stack of 2yr. Red oak (I know,I know 3 is better but this is burning great) and the cat probe has no trouble getting to 1500 but only stays there for maybe an hour and a half then starts to fall off. It will gradually drop to about 800 after maybe 3-4 hours and hold that temp pretty much until it hits the coaling stage and drop to around 500. This is over about a 6-10 hour depending on the load. I know I'm leaking some air in around one side of the door and I have a new gasket ready for a stretch of warm weather so it won't shut down as much as I would like. For you cat burners, does this seem like a normal cycle for you? In particular I'm interested in the length of your peak temps.