Boards are made of natural materials. If you bought something from 2000 and literally never rode it today it would ride like poo. Board materials break down over time regardless of how often its been ridden. A 2005 that has been ridden at least 60 days is surely smooshy and dead.
I have a hard time believing this. The only natural material in a snowboard is the wood, and if wood broke down by just sitting there all our houses would fall over. The FG and resin aren't going to degrade noticably on a board that was bought and stored for ten years.
I'd be willing to bet that if I bought two identical boards today, and rode one this season, and put the second away in a closet for 10 years and brought it out for a season, that I wouldn't notice the difference.
Luckily I have no organic materials in my board so the fountain of youth it does not need...