Jon, I think you're focussing on a few horror stories; everybody can think of at least one.
But for every horror-show (like the crosshairs falling plumb off the plane in a Bausch & Lomb 4X), there are a million cases of no problem.
And my uncle's problem happened in the early 1950s. In my 50 years of scope use, I've never had a problem. At all. And that's somewhere over 20 different scopes. Fixed power. Variable power. El cheapos. Expensive critters.
The problem you're worrying about? Well, you've most likely got a higher probability of flopping over dead from a stroke, or getting cancer.