I hope the built in tc is very durable , and that you can use it many thousands of times before it wears ...
I never bought such expensive lenses, but seriously if you are spending over $10000 for a lens, they better be "very durable" and you can be certain that "you can can use it many thousands of times".
Just out of curiosity, when you say "before it wears", what exactly do you mean? what kind of wear are you talking about in an inbuilt tc?
5D MK III, 16-35/2.8 L II, 24-70/2.8 VC, 24-105/4 L IS, 70-200/2.8 L IS II, 100/2.8 L IS, 40/2.8, 50/1.4, 85/1.8, 150-500 OS, 600EX-RTx2, ST-E3-RT, Rokinon 24/3.5 T-S, D7100+18-300 VR, YN568EX, 055CXPRO4+468MGRC2, 190CXPRO4+322RC2, Gorillapod Focus+496RC2, CamRanger, B+W filters, Konova K3/31.5 etc