Bought 96 GM w/57k When should I replace intake manifold?

Just bought a 96 Grand Marquis w/57k miles on it. I've heard about the intake manifold recall. Just curious as to when I should replace it? I don't want to wait too late. Is there a mileage marker, etc. when these generally go out?

Thanks.

Basically they are good until they go bad. My 98 went just over 100000 miles before it started leaking (2 months out of the extended warranty). It depends on how you drive. Did you ever notice the police cars sitting on the side of the road at an accident? Did you ever notice the hood was open? Because the cruisers sat idling a long time the hoods were opened to keep the manifold cooler and keep it from cracking. I still get cranked that the "fleet vehicles" were covered under warranty and the extended consumer warranty on the manifold was the result of a class action suit.
PS...I fixed mine with a 2006 GS.