How long will a Rolex continue to keep its depth rating?

[VonSomething]

I've often heard people talk about vintage Rolexes and how they would keep them away from water.

In my opinion, shouldn't a watch continue to be as waterproof as it's rated for, as long as it's serviced and kept in good condition?

Or does steel and tolerances shift ever so slightly over generations that at one point a 100m WR rated watch will only make a 30m WR rating, even with new seals?