I was rereading HP Lovecraft's The Call of Cthulhu lately, and the quote from the Necronomicon jumped out at me as a very good explanation of exactly why cryonics is such a good idea.

(Full disclosure: I myself have not signed up for cryonics. But I intend to sign up as soon as I can arrange to move to a place where it is available.)

The quote is simply this:

That is not dead which can eternal lie,

And with strange aeons even death may die.