My Leupolds work fine. So do my Weavers, Nikons, Bushnells, Redfields and Bausch and Lombs. I have had several Tasco's a couple Bushnells a Simmons and a Sightron fail in one way or another but none on a hunt yet.
And with certain scopes that are built to actually hold zero and function properly (NF, SWFA, LRHS, DMR, etc), we can minimize the chances of having a scope failure when it counts, whether on or right before a hunt, during a match, etc.
Since I haven't had one fail me on a hunt yet I'm not terribly worried about it. Even if I did miss a deer because my scope failed it wouldn't be the end of the world. I'd go home, grab another rifle and get back out there. There'll be another deer to shoot at before long.
