I have two Petras (different sizes). My 67 has something like 1000 jumps on it and is pretty clapped. It has had a very hard life, jumps on sand and very abrasive landing areas, it has patches and is a lovely grey colour (desert white). I can confirm that it definitely performing worse than when it was new. I can't get the same recovery I used to get it and it feels like it stops flying a little sooner.
On the plus side it is even better for XRW
The material itself does not show any signs of flaking
I have also had 3 other sail canopies, two jvxs (79s that I owned at the same time) and an experimental wing that did not go into production, they were all built with different versions of sail. One only lasted 300-400 jumps before it was very clapped out.
The first generation sail canopies were probably the longest lasting, it lasted more than 1k jumps with no real change in performance - but was ridiculous in size (and weight).
The new sail is pretty awesome (all things considered).