You might consider propagating from this stock as it obviously has great genetic quality to withstand that many seasons without rotting away. There would still be plenty of neck scars left over to show an older than average aged roots and remember legally we just need to have a minimum of 5 bud scars showing.
By removing a section from the top down in one piece to include the following biomass:
next seasons aerial shoot bud and stem scar material along the neck down to and including
at least one adventitious root needed to feed the transplant.
Just think of the number of seeds you can produce in the next few years.
You can still sell the main tap root for a good price and you didn't even have to destroy the whole plant to do it.