Your PortKey is valid for a maximum period of five years. The expiry date is printed on the card as 'valid until'. Your employer can renew your PortKey. If you extend the PortKey due to expiry, only the XS-Key setup fee will be charged.
If the card is not renewed it will automatically be blocked and can no longer be used. If you want to start using a PortKey again after this has happened you will have to apply for a new card.
Simply follow the regular application procedure with the associated production fee.