According to several people around here and on Micechat, yes, you can use your unused ones that you won last year or last Feb. or whenever, to the end of the year. It's a recent management decision due to the fact that sometimes they hand them out on slow or rainy days when the dream FPs are really kind of worthless, because all the rides are practically walk-on. So they're supposed to accept them now, if the tabs are still attached to the body of the dream FP. Please don't quote me on this, I'm no expert. Just what I've read here and on MiceChat.

But I see the PP above did have this experience!
The only ones I saw on e-bay when I looked yesterday was a few with 6 days left and the current bid was something like $35 each. I did see an offer that was deceptive; it was a parkhopper with one day left on it and it said "with fastpass" -- the description said that "fastpass is included with admission" which is just a stupid sell on a regular ticket because FPs are availabe to ANYBODY with admission, of course, if you bother to go pick them up.
For the poster wondering what dream FPs are: Year of a Million Dreams; you know-- they send out CMs to hand out little prizes in random places throughout the parks. People call it "getting dreamed." There's a thread on the first or second page about this, asking people to tell how and what they were dreamed with. You might get special Mickey ears, a lanyard, a night in the Dream Suite (one family a day!) or-- a Dream FastPass. They are blue cards on a lanyard that have a tab for each FP ride on them, you get one for DL and one for CA. So basically you get one FP for each FP attraction in the park, to be used that day. They snap off the tabs at each attraction as you go in.
People have gone multiple times a month and never saw the dream team; other people have been dreamed multiple times on their trips. Often it's easiest to find the dream team early in the day, before 10 a.m. They often stand at the exits to rides handing them out to people who are just getting off a ride. Some people haunt the CM doors, watching for them to come out, and stalking them to see where they go.
HTH!