I've got a 550 Griptillian that I beat the crud out of. I flick it as hard as I can every chance I get. It's my beater knife for work.
I figure if I'm gonna beat a knife to test it's lock design, let it be the $50 one instead of my $100+ axis models.
So far, the knife has not been apart, so I have not really been able to look at the wear under an eye loupe. I've been snapping it as hard as I can several times a day since I got it in late May, and the lock is only about 5/8 to 3/4 of the way to the max adjustment. I still haven't brought myself to spine whack it. That would put a little more stress on the axis bar itself, and possibly bring the bar over farther in the locked position. I figure that there's a better chance I'll break one of my knives from flicking it open than from an actual use of the knife. Most of the stuff I cut at work is paper, plastic, shrink wrap, rags, and rubber.
I rarely flick my 730cfhs, 735, 721, or 942. But for some reason I love to snap that 550.
John B.