I've towed my quad trailer only locally since getting my skids. The total weight of loaded trailer is approx. 2,500 lbs. So far, I haven't had any problems with overheating. I guess the real test will be when I tow my qauds up to the mountains next month.
Both diffs, the tranny, and the t-case are now running synthetic fluids. Supposedly, synthetics help reduce friction which should help keep the operating temps down.
I have read that some people will take their skids off when they tow for long distances.
Yesterday I towed a trailer with about 5000 lbs total weight (trailer and firewood) about 40 miles and had no troubles. The clutch did smell a bit when I was backing it up over the curb with surge brakes on the trailer though. I have all under skids minus the gas tank.