My buddies 98 LGT had them go around 120K - Only changed coolant around 60K
My mom's 02 TS went around 89K - Never changed coolant
My buddies 99RS went around 90K - never changed coolant
My Brother in laws 02 RS went around 120K - coolant flushed once.
My 04 TS is on original - flushed coolant at 30k, 60k no issues whatsoever, 101K on the clock.
I blame prolonged coolant use, it does eventually breakdown and turn acidic.