Research has shown that if you get at least 25 minutes of exercise per day you could add 7 years onto your life.
But there's no guarantee that walking will make you live longer. You could die of some other disease or get hit by a vehicle or something and then that walking could kill you.
But walking is good for your health and if you stay active into your old age you have a good chance at staying mobile and living longer maybe even to 111 and beyond like that 111 year veteran.