Back in November 2012, i bought a vita on black friday which came with 3 voucher codes for ps plus. each code provided 1 month of ps plus which added up to 3 months total. I used one of the codes when i first got the vita but now i am first trying to use the other 2 codes and it is telling me that they are both invalid when i should still have 2 free months of ps plus left. WTH? can they expire or something that I was unaware of?
Yes. Playstation Plus voucher codes do have expiration dates. The price of Plus can change at any time. Sony will only commit to providing the subscription at a particular price for a limited time. You are not intended to stockpile Plus codes for future use. That would allow you to avoid future price increases, if any occur. Those were intended to be trial offers anyway, after which you were expected to pay for a subscription; although the number of trial codes that you can redeem is not limited to just one. Sony promotions are always for a limited time. The retailer did not pay anything for those trial subscription codes, so it had no problem with giving you multiple ones; which was probably not what Sony intended either. You didn't lose anything that you actually paid for.