There is no set time or mileage at which a transmission will fail. There are just too many variables. How it's driven, city, highway, and how well it is maintained.

If it is still working normally, keep it serviced frequently and keep going down the road. If it ain't broke, don't fix it.

The main destroyer of a/t's is heat. For every 10 degrees above normal fluid temp the life of the fluid is cut in half. The fluid temp is not determined solely by ambient. Fluid temp will increase a little in stop & go driving, and a LOT when towing.

Hope this helps.

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2001 SLK 320 six speed manual
2014 Porsche Cayenne six speed manual

Annoy a Liberal, Read the Constitution

would you consider slow moving traffic, driving solo, A/C on and engine temp gauge at 98-100*C as transmission fluid torture? My tranny fluid is pretty pink and clean but shows overfilled when the system temperature gauge is 100 and shows below the cool mark when the car is started from cold in tx mornings

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2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)

Slow moving traffic like a traffic jam on the freeway won't be too bad, but full acceleration stoplight to stoplight on a hot day would certainly warrant more frequent fluid changes than would pure highway driving.

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2001 SLK 320 six speed manual
2014 Porsche Cayenne six speed manual

Annoy a Liberal, Read the Constitution