change tranny fluid again??

2004 Yukon XL Denali, 6.0, AWD, 84000 miles. I had the fluid/filter change we talked about back in March (and a rear end fluid change and transfer case check). In June I hooked up our 27' trailer (about 7000+ lbs), and we went on a 3600+ mile trip through Nevada, Idaho, Montana, South Dakota, Nebraska, Wyoming, Utah, and back through Nevada to the Sacramento area. Lots of long gentle grades, and plenty of steep mountain highways, too. Every time I used the cruise control it would kick way down so the engine was churning at 4500-5000 rpms. I quickly got off the gas and tried to keep it around 3000-3500 rpms on inclines of any type. Often I just kept it in 3rd gear so it cruised easily at about 3000 rpms. I am using M1 EP oil (fresh at the start of the trip).

Question: even though I had the tranny fluid changed at about 79-80,000 miles before the trip, should I change it again or do a flush and replacement of all the fluid after that much strain on the tranny??? Or, another fluid/filter change? Or, just wait until it's due again if we're not pulling anything?