Just how stupid was Ar-Pharazon?

[Hot, crispy nice hobbit]

I don't think Ar-Pharazon died. He and his men were imprisoned until Dagor Dagorath, the last Battle.

But Ar-Pharazon the King and the mortal warriors that had set foot upon the land of Aman were buried under falling hills: there it is said that they lie imprisoned in the Caves of the Forgotten, until the Last Battle and the Day of Doom

So you might say that he got the 'Immortality' he wanted.