My dog Pumpkin lived to be 17. Towards the end of his life he had cataracts and was mostly deaf. I think he had arthritis too because he stopped lifting his leg and began squatting. Even so, he would follow me around everywhere. We brought a puppy into our home when Pumpkin was old and I think it sort of added a little excitement to his older years. Dogs do not forget the love they have received all their lives. I am sure Rufus knows you that love him. Try not to worry so much.