This begs the obvious question. Why not find a young farmer and help him by renting your farm to him? If every retiring farmer for the next 10 years has his farm custom farmed how will new blood enter the business? Did someone not help you get started 40 some odd years ago? Maybe not but if not, yours was about the last generation to be able to start without some sort of help.

You've built something. You can either go the custom farming route until you no longer can or you can help someone continue on what you started. Your choice.