The answer to that question would be in the Bible.
Not necessarily. Some holy people die young. We Orthodox read a Scriptural verse about that (not part of the Protestant Bible), on Saints’ days. I cannot locate it right now. It’s about God taking some holy people young, before they can become corrupted with sin.
But there are other Scriptural verses—for example—about Nebuchadnezzar going mad. Evil can destroy the mind. But we must not judge others in that regard.