Mine has been in about 2-3 yrs and probably about 30k how long should it be good for before change. The car is mostly stop and go city traffic if that makes a difference as well.

Here is what they recommend.

SERVICE LIFE
AMSOIL Synthetic Automatic Transmission Fluid is recommended for use up to 50,000 miles under severe service* and up to 100,000 miles under normal service* or according to the vehicle manufacturer recommended intervals, whichever is longer. AMSOIL recommends thoroughly draining the transmission and flushing with new AMSOIL ATF to achieve a minimum 90% purity of new transmission fluid. Drain intervals may be extended further with oil analysis.

* As defined by the vehicle or transmission manufacturer.

SERVICE LIFE and other info can be found here (http://www.amsoil.com/redirect.cgi?zo=34396&page=StoreFront/atf)

I would say you can go many miles yet.

Amsoils definition of normal and severe
Normal Service defined as - Personal transportation vehicles frequently traveling greater than 10 miles at a time and not operating under severe service.

Gasoline Engine Severe Service defined as - Turbo/supercharged engines, commercial or fleet vehicles, excessive engine idling, first and subsequent use of AMSOIL engine oil in vehicles with more than 100,000 miles, daily short trip driving less than 10 miles (16km), frequent towing, plowing, hauling or dusty-condition driving.

Product Recommendation and Drain Interval Chart (http://www.amsoil.com/lit/g1490.pdf)

My Town Car gets a complete flush every 40k whether it likes it or not.
All my other vehicles get a 50k flush. Makes record keeping easier when you run a fleet at home.