Heh, I just watched the Season 2 finale. When Don says goodbye to Timmy before leaving the lair, he says, "If we don't make it back you'll defrost in, I dunno, maybe 70 years or so. Hopefully the world is a better place by then."
I wonder if the writers knew back here that the world would be destroyed 50 years in the future.
It's kind of funny rewatching old episodes and seeing all these hints to the future, now that we know what happened. And of course Timmy just dies.