Why doesn't Gilgamesh take siduris advice?

"Gilgamesh, whither are you wandering? Life, which you look for, you will never find. For when the gods created man, they let death be his share, and life withheld in their own hands. Gilgamesh, fill your belly. Day and night make merry. Let days be full of joy, dance and make music day and night. And wear fresh clothes. And wash your head and bathe. Look at the child that is holding your hand, and let your wife delight in your embrace. These things alone are the concern of men."