I just received my order of 1/72 DC-4 decals from Vintage Flyer Decals. When I opened the envelope there were quite a few sheets of decals, including some extras.
Inside was a note explaining that when the vendor is less than pleased with the printing of any of the decals, they reprint them and include both. It was easy to tell which were the replacements by the layout on the sheet, but man, visually I see no difference.
I thought that was a very nice gesture.