No, they don't, but at least it solves the OP's more immediate problem of her current vouchers expiring in 48 hours or so, and by buying vouchers from large, well-known retailers which will likely be used, redeeming them for cash won't be a primary concern. For example, Coles/Myers gift vouchers can be used at any store owned by that company, which covers a huge number of different retailers. You can even use them to buy groceries, so they certainly won't go to waste.