Don't know about Campy sealed bb's in general but my Chorus triple bb has 11,000 miles and has no signs of problems. A Shimano Octalink sealed bb on another bike has 22,000 miles and runs like-new so I'd expect Campy to last at least that long.

If your bb still turns smoothly and has no play at the crank arms, I'd just keep riding it. Replace it only when there are clear signs of trouble.