I'd agree with babymog, and say it's a complete crapshoot anywhere past 150K. Fluid/filter changes on time are the biggest key to winning the longevity battle. I'd imagine that keeping transmission related vacuum leaks in check also helps. Flaring and harsh shifts can't be good for long term transmission health.
I just did a fluid/filter change last week, it had been a (HARD) 50K so I was a bit overdue. There wasn't even a speck of clutch material to be found. Reverse is still snappy. I don't see any issues for the next 20-30K, at least.
