the red giant phase is temporary. it is shorter than the billions of years a star spends on the main sequence. soon (in only hundreds of millions of years) red giants will start to fuse helium to make other elements like carbon, nitrogen and oxygen. some of their outer layers will blow away, leaving interstellar gas and dust circling the star. in time, most red giants will become white dwarfs. very large red giants become neutron stars or black holes.