I had a d16 on my jet mini for a long time. It will work but the lathe don't have enough balls to drive it. Plug turning minimum is the bigger jet and for something like what Billy wants to do with 3.5x3.5x37" billets he needs a bigger machine with variable speed.
2x2 birch at 3000 rpm on Eegore to do a turning in well under a minute. Want to buy it Bill?
Age is relative and doesn't matter on these when you take care of them. The only thing that ever wears of them is the teflon blocks. And you're getting a brand new set of replacement blocks with the duplicator. That unit is about 5 years old.