The only mainissue I could see for failure would be the gasses in the scope wearing out and foggin up. Unless it is really abused intentionally I see no other failure than this. I have seen the cross hairs fall off from poking them, But it took some force to do so. I all so seen the MOA screws tightened down to where the scope could not be sighted in after that. But these are intentional abuses I have performed my self on scopes.Once my sling broke walking down the tracks,Not intentional. And my scope took a nasty hit off the rail. It bent thetube.I couldnt see the cross hairs from cross up. It was screwed.