How many years will the earth be destroyed?

As the sun ages, it will begin to expand. While the sun will be, by all astronomer's estimates, around for another 4.5 to 5 billion years yet, it will have expanded to the point where the increased heat will boil off the oceans and make life on earth untenable in about one billion years. Mankind - or mankind's successors - will have moved on long before then, in all likelihood.