Updated the OP with links.
Yes, those coins should expire next year at some point. But it's a game-by-game basis, and right now only Super Mario 64 DS has expired.
Crud, I guess that means I lost those coins (unless I never registered it since maybe the program wasn't available yet).
I'm not seeing any warning on the Club site about when my coins expire.
Looking at the stuff, I'll probably never actually get any posters put up though the Zelda ones and one of the Mario ones are pretty cool.
I don't know, maybe a set of folders and bookmarks. I could conceivably use those I guess. Though I hate that they'd wear out in normal use (I'd like something more permanent with my coins darn it )