Why does the National Association of Certified Home Inspectors (NACHI) advise that vinyl siding will last for 60 years?
Because the new stuff (10-years or less) probably will. It's been tweaked to account for almost all of plastic's shortcomings. But, you'll always have to clean it with Paint-Effort practices every 5-years and it will blow or break right off someday and kill or injure you or someone else.
The older vinyl's lasted only 20-years, they cracked, split, warped and faded. I get 15-years out of most anything I paint and it never looks dirty, moldy and ugly like vinyl. One thing that plastic's proven is that it dries-up, turns brittle and then lets loose. It's the worst I've ever had and I won't ever get it nor keep it again...I finally got it 7-years ago, Aluminum and Steel are amazingly better.