I have a 9500 that came from the factory with the black steel rasp bars. They only last 3-4 years. We replaced them with the chrome bars from Deere. They have been in for about fifteen years and still thrash good in tough conditions. I looked at replacing them last year but they show little wear.
In the first few years it was running 800-900 acres of mostly soybeans with some wheat and milo as well as some custom cutting. The last few years we have been harvesting 150-200 acres of corn and 300-400 acres of beans and some wheat also. We have probably covered 8000-9000 acres since the bars were replaced. We have never had any breakage but we also have no rocks so that may make a difference. Most machines in my area run the chrome bars.
Now we are getting somewhere. I know there are better bars out there than the ones offered by John Deere. No doubt the chrome bars are better but I constantly see on here people talking about better brand concaves and rasp bars.