Well, being one of those skaters who is "harder" on boots than average, I think it has a lot to do with overall skating power and knee bend, deep edges, etc... and nothing to do with jumping. It's not an issue with fit (my current boots are probably the best fitting skates I've ever had, even compared to when I had customs) as much as just needing a stronger boot than some skaters do.
Just because a skater isn't doing triple jumps, doesn't mean that they couldn't require a boot stiff enough for them... I would be extremely under-booted if I was in a boot rated for my "level" (which is singles, though I'm working on my axel and some doubles). I skate in boots rated for triples and quads (Jackson Elite Plus, stiffness rating of 85), neither of which I am doing, or will ever be doing
I have no problem with knee bend, even when my current boots were new, which is really the biggest concern with very stiff boots - without the ankle being able to bend sufficiently, the skater does other things to compensate, many of which can lead to injury. My current boots are two years old and still have a lot of life left in them, but I don't skate as much as some do - my schedule varies a lot, but I rarely get in more than 5-6 hours a week on the ice, some weeks are closer to half that.
As far as screws coming loose, I've never had an entire blade come loose nor have I had many problems with loose screws (I think I've had two in all the years I've been skating). I would think that poor blade alignment or uncorrected pronation/supination could contribute some to those problems.. if there is extra force being applied to the blade sideways I can see how that could be repeatedly pulling screws loose.