When is the world going to die?

The sun has about 4.5 billion years left before it's lease expires, but the earth will be uninhabitable - incinerated, in effect - well before that, but you don't need to worry right now. Most astronomers thing that life on earth will become untenable (because of temperature rise as the sun expands), in about 1.5 -1.7 billion years. In about 3 billion years, give-or-take, the earth will be inside the sun - or what's left of it.