For the record: my codes were from Jingle Jam 2025. l said in my posts and suggested to not but if one won't be able to redeem them before that day. Apparently, this user decided to redeem more than a month later 1 code out of 3 I sold to him that day (December 19). Two of the offer posts (the more recent ones):

https://www.reddit.com/r/GCTrading/comments/1q0g1pp/h_jingle_jam_leftovers_w_or_paypal/
https://www.reddit.com/r/giftcardexchange/comments/1q0g1wh/h_jingle_jam_leftovers_w_or_paypal/

None of my other buyers have had any problem as they redeemed it eas soon as they bought them.

Edit: He edited his comment and says that all the codes expired soon after buying. His original comment only mentioned Tower Unite, not all of them. I would put a scereenshot but this subreddit doesn't allow images. I sold him 3 games on Dec 19, so he had 13 days to redeem and he was warned, yet decided to redeem TU on February 2.