The parts i select to send are the ones high in demand and some to a point where the cars start to stop for want of the same. The syncro rings are one such item. Even without abuse they have a life and are meant to be replacable. You may still be able to shift with worn syncro rings but you'll hear a thud or a crunch
Ihsan has done the tranny rebuilds but Khalid is more current with the task. Poor guy has been trying to keep the bugs on road with old syncro rings salvaged from older trannys.
Ultimately its your call if you want to buy or not. I usually keep a part even if I don't need it right away but that means blocking some cash that you could use elsewhere...Ah the joy of finding a part when you need one..