I had a villager who was just about to become a Master Farmer and he turned elderly. I just kept dropping him in the field and had him planting crops, because it is something that takes a relatively short time and he can do over and over again without moving alot. Another thing I did with him is if he went to the ocean and tried to fish, I waited until I saw the message that he had improved at farming (which comes after the 3rd dive) and the minute I saw the message, the time it would take him to get back to the food bin would be wasted time. Since he was elderly and I had enough food, I just drop him back in the ocean. Saves time and made him my 2nd Elder at 63.