I think some of it is the paint they use to kill internal relections. Been kinda-sort looking at nice old Balvar 8s, but internal debris is one hazard with those apparently, besides the dearth of mounts for rifles made after the Nixon administration.
Agree that twisting , especially on scopes not built to take it will wear stuff, but that's the price of doing that business. Best to go with one designed for it, keep an eye on things, and send them back as needed. Everything has a service life; silly to expect anything with moving parts to last "forever" without maintenance. For my field use, a multi-point reticle makes more sense anyway, but others have other situations that are best met with knobbery©.
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