Personal stockpile's made 500 years old (5)
I believe the answer is:
hoary
'years old' is the definition.
(thesaurus)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for hoary that I've seen before include "White or grey, or old as of joke" , "Venerably grey" , "Like an old joke" , "Grizzly - ancient" , "Having grey or white hair" .)