Are wizards immortal?

[Farael]

Originally Posted by The Sixth Wizard

But Saruman, after his incarnate body was killed, looked to the West for pardon, and was apparently destroyed completely!

I believe that he was not destroyed for I'm not sure the Ainur could be destroyed as we can, but maybe he was rejected from Valinor and then cast into "the void" (although that's rather akin to destruction) or perhaps as he was unable to take physical form and whatnot he wasn't quite destroyed but he was unable to interact with the world anymore... so for all intents and purposes, he's as good as gone.

But that's just speculation, I'm sure someone more knowledgeable than myself will soon adress that point much better.