The only way to make any automatic transmission last is to service it regularly. In most applications 50,000 miles is an acceptable serivice interval, however in rough service applications you should consider cutting that in half. Having been a mechanic for more than 30 years I can tell you that I have seen it all. Machinery simply will not wear out if it is kept lubricated with good, clean lubricant. You can never change oil 'too often'.
On the flip side, however...if you ever find yourself in possession of a vehicle with high miles that has never had an auto trans service, the very worst thing you can do is change the oil in that transmission. Chances are it won't make it back from the post oil change test drive...lol. I have seen this happen dozens and dozens of times. So much so that I actually make people sign waivers when they want me to service their high mileage auto trans's without any known history.