Just had a look, wasnt aware of these codes, but they have two prices, how does it work to get the lower price?Existing prices are still valid at the moment so you can extend your current sub if necessary. That said it's probably still cheaper to wait till they discount it as they usually do a few times a year.
Also, a reminder not to buy games or subscriptions using a debit/credit card on the PS Store, you'll save about 15% by using wallet top-up codes from ShopTo etc.
Shopto I stopped using a few years back as my account vanished without explanation.