When you get into what has been termed "old age', you are looking toward the end of your life. And the verse from Isaiah is a true comfort, because our God tells us very succinctly, He is with us. He will sustain us. He will carry us. He will rescue us.
But the even better news is that verse applies to every one of us, no matter what our age. God made us and will sustain us. He gives us strength to make it through whatever this world throws at us. Give thanks to Him for all that he does for us.
++Richard