If the media is sealed in a cake box and stored in a warehouse somewhere, it should still be perfectly fine. A month or so ago, I bought some Sony YUDEN000 T02 media that was made in 2004, and it burns better than any of the new media on the shelves in the US and even the unbranded TY from Rima. My Maxell MAXELL 002 were likewise sitting on the shelf for about two years. I dug through Office Depot's shelves and found it in the back. They burn very well too.
With that said, I would avoid 4X media now. I don't think it's the time degredation so much as the scarcity and, as a result, the lack of firmware support. I don't think it's too presumptuous to claim that the strategies for these media are no longer being worked on by current drive manufacturers. Who can blame them, really? Almost no one uses 4X media anymore.