官網FAQ: If your Pay-Per-Ride MetroCard expires, you have two years from the expiration date to transfer any remaining money to a new card. Within the first year after expiration, bring your expired card to any subway station and ask the agent to make the transfer. After that time, the expired MetroCard must be sent to MetroCard customer claims. Ask the station agent for a postage-paid Business Reply Envelope. http://web.mta.info/metrocard/problems.htm#expired
If your Pay-Per-Ride MetroCard expires, you have two years from the expiration date to transfer any remaining money to a new card. Within the first year after expiration, bring your expired card to any subway station and ask the agent to make the transfer. After that time, the expired MetroCard must be sent to MetroCard customer claims. Ask the station agent for a postage-paid Business Reply Envelope.
http://web.mta.info/metrocard/problems.htm#expired