Transmission woes...again

The factory transmission lasted 205,700 miles. I replaced it with a BTS at that point. That one lasted to 285,988 with just 80,298 miles. I sent it back to BTS for fixing. Now that one is gone at 425,000 with 139,002 miles on it. I haven't abused these transmissions. I've put in the newer larger oil coolers and I rarely see temps about 160...most of the time I'm in the 140 range due to the colder area I live in. I've kept up consistent fluid and filter changes every 30,000 miles and have only used BTS recommended Shaeffers All-Trans synthetic fluid. I've probably only towed a total of about 2500 miles in all the years I've owned the truck. Its been my daily driver.

Recent saga is that it was running fine up until this morning when out of nowhere it will only engage into reverse. Any forward gears it will just rev up and not move. last summer out in Arizona it puked out fluid out of the transmission just sitting after a day in the heat while visiting there. Its done this before with the last transmission. Never leaks until I get into Phoenix in the summer months and parked it. Leave it for a day or two and there will be a large puddle of fluid under the truck. I fill it back up and everything is good. It has lost about 2 quarts from this heat related expansion.

I thought I was doing myself a favor by going with the BTS transmission but my experience has not been very good up to this point. I'm not sure what to do at this point? What are people recommending for transmissions these days?