My two remaining XCR rifles probably have about 8k through them both without a issue, serial's in the mid 7k and 8k range. The others I've traded or sold never had a problem with an op rod, serials in the 4 through 7k range.
I don't know, but did the op rod change per the "generation update"? (at this point if something wasn't broke, not certain why RA would want to change it, but sure they had their reasons).
Just trying to stay away from the "sky is falling" mentality