Visa tokens expiring

I had a couple of Visa cards from march and April from swagbucks that I went to redeem through the visa website and it says the tokens are expired. I had never claimed them from swagbucks until now because I did not have anything to use them on. I thought they were good for six months and the tokens were maybe good for longer. I don't see anything stating anything less than six months when you go to redeem a Visa card. Has this happened to anyone else? Or did I miss something? Thanks,