It will depend on how many tractors were sold and how the parts move. For example if Kubota finds that they haven't moved any parts for say 3 years, or maybe sold only 3 parts in 5 years, they may no longer supply the part. They may, howver, run into other issues. Kubota doesn't make all the parts going into their tractors - they are dependent on outside suppliers. Those suppliers go out of business, get bought up, etc. Therein lies a major problem - how to supply parts when you do not own the design and have no control over your source. I have a 1929 Case CC sitting at the end of my driveway that I would love to having running again but apparently the person who owned the farm from where I salvaged it made some bucks by selling parts.