If the tires are kept in a garage out of the sun, I'm not so sure I believe in the age thing up to a point anyway.  When I bought my 85 Kawasaki in 2009 with only 1k miles on it, the original tires looked great.  I actually rode it 300 miles or so before changing them.  I still have those tires.  I thought about advertising them on ebay just in case someone is trying to restore a bike to original condition for collector purposes and they would appreciate oe tires.  Of course I wouldn't trust old tires for an all day cowpuc run of 100mph across the desert.