time
Well, I don't wanna sidetrack the topic, but I think the lifespan of a budget scope depends much on just how much hunting and shooting that rig will actually do, and the conditions.
HUNTER A has a two week deer season and a one deer limit, and gets to hunt the opener, and a couple of week ends maybe a PM or two after work, say 5-6 hunts a year......check the zero with 2-3 shots factory ammo a season...., then back in the cabinet till next year, that's not a lot of use. The gun rides to a covered blind in a padded case, where it sits in the sheltered corner 'till he might get a shot, that's a pretty soft life. That's not thirty years either, that's about 150 hunts, which is about 5-6 months of "use" at best over the course of 30 yrs.
HUNTER B has a season that last 3 MONTHS, with multi deer harvest and he does some hunting out of state as well. In a given year, he gets 50 hunts in, and he hunts hard, bad weather, on foot, from exposed stands. He also reloads, and shoots for group, and practices a bit with ol'Betsy. He gets afield 1500 times, 4-5 YEARS worth of use, over the course of 30 yrs.
I do not intend to belittle or berate , I simplify and exaggerate for the purpose of comparison, but which hunter uses a scope harder, and is more likely to have a budget scope fail?