I would have thought an older Ryeland tup may well be on the fatty side, compared to a Shetland. We have eaten our older Shetland tups (at the end of breeding season mind), but I also do not see anything wrong with sending older ewes and tups to the cull market.
It is always easier to keep a ewe as a lawnmower (I still have one of my now 10yo homebred ewe - Shetland with a full mouth!), but tups are just too difficult. Unless you show I would have thought meat is the best way to go - if you sell him too cheap the new owner may get more for it in the cull market.... just saying.