David, I wonder if you haven't touched on the real essence of the thing here? The perceived ability of the type of knife.
We've all seen those photos here of old, very old well used knives with the blades sharpened down to a couple of steel toothpicks. It took decades of use to do that, and that meant the owner took care with his tool. It got treated like a cutting tool, and well maintained. It was heavily use, but not abused. A lot of our grandfathers did not have the very large amount of disposable income that we enjoy today. Also they were not knife nuts. They looked at a knife as a daily tool, and most men took care with their tools. By contrast, todays knife market is filled with knives that are advertised to be more than a knife, the great hyped zombie killer or pry open a Brinks armored car door. This is going to lead to some 'over use' by enthusiastic owners having great faith in the claims of the manufacturers.
I know of two young men that have broken a knife because they were abusing them. One was a ZT something that was being hammered through something. The young man was indignant over it, and stated that it was not even that big a hammer he was using. The other one was just as bad, the knife being leaned on and the lock gave out, causing the young man to be a patient at a hand surgery clinic to try to get the severed nerves and tendons working again. I can only wonder if the young men had grown up using slip joints, would they have made such a bad mistake?
By comparison, the men I grew up around had the same little slip joints for many years. They didn't go buy another pocket knife until they wore out the one they had, or it got lost, which was not often. My boss Ira had the same little brown handle jack for well over 20 years. Heck, my dad received a Case peanut from his mother when leaving home just before WW2, and he used it until just few years before his passing from leukemia in 1981. He used it gently, never abused it, stropped more often than sharpened, and was careful with it because it had sentimental value. He only stopped carrying it when arthritis made it hard for him to open it, and switched to a little Christy knife. If the peanut was not enough knife, then he'd use his cut down machete bushwacker tool he'd made. A true follower of the 'right tool for the job' line of thought.
Today, modern knives are marketed as the 21st century answer to King Arthur's Excalliber. And they are tougher and stronger built knives. I think this will lead to many knives being abused by their owners in the belief that the knife was designed to handle it, so it will be beat on. So I think we'll se a higher degree of damaged locking folders vs slip joints. But if each one, the slip joint and the lock back, are used as a knife only, I don't know if you will live long enough to see a difference. Used as a cutting tool, each one will get the job done, and most cutting jobs are not heavy duty. Aside from the odd Navy SEAL here and there, or the Walter Mitty type, how many of us are going to be in a situation where we will need to abuse our knife? Treat the knife as a cutting tool, and I don't think you will see any difference in service life of a slip joint vs a modern folder.
Carl.
