Hello Brad, this is the GEC number 15 I put through it's pass for a year. It is now in the hands of my nephew, who will do the same. I used ti fro breaking down boxes, fishing and cutting bait, cutting line used for crab pots, opening boxes and plastic blister packages, and many other things. It was used, but not abused, and that is the key.
A traditional pocket knife will do what your modern ZT will do as far as real world cutting. It's the cutting edge that does the work, and used right, you will be able to do anything you really need to do. Look at it this way, our grandfathers, and their grandfathers before them did real work with these knives. A freight wagon driver getting a heavy loaded wagon over Raton Pass, a cowboy pushing a few thousand head of cattle up the trail, a sailor on a whaling ship, all used slip joints with no problem. They have been around for centuries for a reason, and that reason is they work. A thin blade of good carbon steel will do a lot. Look at the Stanley utility knife used on most construction sites. The blade is all of one inch long at the cutting edge, and about as thin as a a razor blade. Yet it slices tar paper, shingles, bags of cement and cuts of the plastic ends of caulking tubes. Very rarely they break. They don't break because it's the edge that does the work. Since 1890, millions of French peasants have used Opinels for everything with good results. And the Opinel is not even as sturdy built as a Case sodbuster or Buck stockman. Or a GEC Bull Nose
The GEC, or any other traditional pocket knife made by a reputable maker, will stand up to what you need. Breaking down boxes and opening feed bags won't even make it break a sweat. The Northwoods stockman I've been using since this past April, has done everything the GEC did with no problem. Again, breaking down boxes after a shopping trip to Sam's club, fishing, cutting dirty jute twine in the garden, opening 50 pound dog and bird seed bags. The carbon steel 1095 blades hold an edge as well as I could wish for. And there's three blades to choose from in one pocket size package.
I spent 25 years carrying a Buck 301 stockman. It stood up to anything I had to do, and I did throw a lot at it. Try a traditional and see for yourself. You will be very surprise at how ell it works. And GEC is some good ones.