[ppbon]

... a man's prostate.
Give it enough time and it will develop cancer.

Even on engines that are driven very hard, with time they will fail.
Just like jake Raby, I've seen that "normal" daily drivers tend to fail sooner than later, but even engines with many, many track miles fail.
Mine was caught in time with 196,000 miles on it (22,000 were track miles).
When I pulled it the bearing was very worn and wobbly and would have failed in a few thousand more miles.

My recommendation to anyone how's worried is ... just do it.
You're purchasing peace of mind.
Once you retrofit, go have fun again.

Happy Boxstering,
Pedro