No - it does NOT! The Expiry date for each card is set from the original date of purchase. You can add funds to your card as often as you like, using your unique reference number, but this will NOT extend the expiry date. The only way to extend your purchasing power is to purchase a brand new Gift Card.
The main benefit of being able to Add Funds to a Gift Card is where several family members or friends all want to collectively provide a Gift. The first family/friend purchases a Gift Card, and then subsequent family/friends can contribute to the overall gift by adding funds to the Gift Card individually, using the card's unique reference number.