I wouldnt worry too much- although obviously coming out of the summer months your tranny ran hotter than it does the rest of the year. The most tell-tale sign of "change it now!" would be brown tranny fluid. It it cherry red when new. I think 30,000 miles is reasonable time to change if you want insurance. I think- but may be wrong- 60,000 miles normal and 30,000 miles severe duty intervals? Of course having fooled with so many vehicles it gets jumbled in my brain. While youre at checking/ changing fluid. Might as well check/change transfer case as well. Besides, its alot easier to do than the tranny