Most of them always have an expiration date and I have already used the shiftcodes for 25, 20 and 20 keys. I also used the shift codes dropped in the last 2 weeks. I NEED UNDERSTANDING NEW SHIFT CODES NECESSARILY. I play again for 2 weeks and have not used the shift codes of the last 4 years. Is there any that are permanently valid? I absolutely NEED Shift Codes!
Here's a list of all shift codes for all platforms. If you've already used all of them, you'll probably have to hope for new codes:
Link to the page: http://orcz.com/Borderlands_2:_Golden_Key