My experience has been that if a scope is going to fail, it will do so right away - like within a few dozen rounds. That's not always the case, but has been so about 95% of the time - again in my personal experience. The main difference between K-mart blister pack scopes and big name display-case scopes is that the blister pack ones are a lot more likely to go kablooey right away. But once any scope has gone a hundred rounds, I find that I can usually count on it.
Glass quality is another topic. Certainly, the $75 Bushnels and Tascos are going to have more clarity issues - chromatic aberration being probably the biggest one, with edge distortion close behind - but I'm honestly not sure that should be worth worrying about in most rifle scopes. Okay, yeah, my target isn't exactly the right color through my scope. And?
Repeatable adjustments are maybe the biggest issue. A really good scope will let you click up and down the same amount all day long, and at the end of it, you'll be exactly where you started. A basic scope probably won't. That matters a great deal in certain kinds of shooting, and not at all for the rest. The great majority of my rifles get zeroed to a particular load and distance, and then stay that way until the heat death of the universe. I couldn't care less about "clicking around the box", etc.
Which is all a long way of saying "Buy a Bushnell. Zero it, then shoot another twenty rounds. If it still works at that point, then it will probably keep working forever. And if you really need great color rendition, put the money you saved toward a really good binocular."