Possible Clues:

• Period for which a stored item remains usable
• How long a product keeps
• Determinant of a 'best if used by' date
• Quiet, Tolkien character might survive this long, perhaps
• Period in which article is for sale
• Left among rotten fish, feel for the time when still fresh
• Lasting consideration
• Olive has a date that only lasts a certain amount of time with bookish type - the type consumed by a biography
• Food's freshness period
• Lasting value?