The cups do wear but I would think that they would last at least 5 - 10 years unless you let one of the bearings wear badly - in which case they soon start sticking and wearing the cups away.
It could be that the cups were working loose through pedalling - I have a bike with good BB threads but the cups still work loose and the solution was ptfe tape. They may have taken a more drastic course to deal with the problem.
So it might be worthwhile looking to see if a little heat will enable their removal.
If you go with the Campy cranks ( which will still work with Shimano BTW) you will also need a wavy washer for the left hand side cup.