jumping into this thread for the first time.
Being in auto body much of my time is spent on my knees, so I can blow through pants rather quickly.
I have tried the Duluth Trading Fire Hose pants and REALLY liked the fit and feel of these things. Tons of movement in them. By far the most comfortable work pants I ever owned.
Also the shortest lived. I bought six of them, and I was through the knees on four pair with in three months. Duluth was kind enough to swap them out for new ones, I got about the same from them. After a third time I called it quits.
I have switched over to Carhart and dont like the fit and feel as much but I am getting better than a year so far with only minor knee holes.
Like you, i'm on my 3rd or 4th exchange. I bought them because of their "we dare you to wear it out guarantee". They have replaced without question, everytime.
They are awesome pants, huge pockets, super comfortable and durable. But not in the knee department.
I suspect it has something to do with the weave of the fabric. Its very durable, but given it has 4 directions, when you rub it constantly against concrete, it has more edges to grab.
A similar effect happens with raw selvedge denim jeans; even though they are heavier OZ, they wear quicker because they are more abrasive from lack of washing.
In this case washing wouldnt make the concrete softer
I got a pair of these recently:
https://www.duluthtrading.com/mens-..._color=BRN#q=flex+pants&lang=default&start=11
The fabric on them is much tighter/smoother. Given the double knee, it seems to be holding up well.
I have paired them with these knee pads:
https://www.duluthtrading.com/neopr...522_color=GRA#q=knee+pad&lang=default&start=1
I can barely feel the kneepads when standing or sitting, but they sure do make a difference when kneeling.
The kneepad makes for less abrasion on the outer layer; as the knee is moving around relative to the kneepad rather then the kneepad moving relative to the ground.
Time will tell.