I've been using this model or it's predecessors to bind on a daily basis for 3+ yrs. I'm about to get another pack, and I have been getting new sets every half a year to 10 months, as I'm a XL, and the single layer of material that composes the back of this binder has consistently worn out in the same place, near the side seams(both left and right sides decomposing at the same rate) and I know that this must be at least partly due to not treating them correctly, but I also believe it is partially due to my body type. I would (if I called the shots for production over there) add a second layer to the back of this model (and, myself, order a size up to 2XL/XXL to compensate for the addition elasticity) and market it for plus sized binding.
Thanks for reading this, at least. Now I'll buy another 3-pack for the next while.