I think the delam issue for a buyer is to be treated as something to address, but not to let it be a deciding factor except if the dollars get in the way.
In a nutshell I don’t think there is a model year range. Having said that, I also don’t think every XLII is a problem. I say that based on feedback from owners who have had their coaches tested and have gotten a clean bill of health.
But nobody should buy an XLII without first verifying there is no issue. However if there is an issue the Prevost service center will forward their findings to Canada where a decision will be made to determine how much “good will” Prevost will provide.
Coaches that have the delamination repair and the rivet cover strips installed are likely to never become a problem. If a coach you are seeking has those repairs, verify the repairs were done by Prevost and you are good to go. I mention verify the repairs were done by Prevost because some repair shops have advertised they will do the repairs and Prevost has made it abundantly clear their process is extensive, proprietary, and can only be done by Prevost personell at a Prevost service center. I have seen ads by others claiming the technicians are factory trained and while that might be true about the chassis, it is not true about the repair process.
But I digress. If the coach you are looking at needs repairs and Prevost has determined the cost and their level of participation then the selling price (your purchase price) will depend on what you and the seller negotiate. Typically Prevost has not paid for the paint work as a result of the repairs so make sure that price is considered when negotiating for a coach.
There is an extensive thread on this forum about the delam issue.