I love to see your father remembering things, It happened too with my Grand mother, she when she was able to revisit her favorite places and relive her daily life pre retirement, she inmidiacly clicked back to who she was at that time and got a lot more retention, speech and skills back, sometimes until the end of the day, so we in her final two decades (She lived 24 years after the doctors said she would die, yeah, not the best doctors xD but the creator does miracles like that from time to time) we tried to push help her to do all she used to do daily and to be there for her the most, so if my gramma could live 20+ years against the "death sentence" that the doctors gave her, I bet your father as a healthy man with a healthy diet, could live a lot more than that :)
Thank you so much.