I have almost 200,000 on my 07 Tacoma with the original ATF. I fully expect another 200,000 miles. It isn't miles, it is heat that kills ATF. I don't tow often and when I do it is less than 3000 lbs. For me changing the fluid every 30,000 miles MIGHT get me another year out of the the transmission. But at some point the transmission will go regardless. Unless someone tows or hauls heavy loads on a regular basis it is probably more cost effective to not change it.
