Hmm, I have a lot more than 21 days on one of my boats made from that same batch of fabric, but I haven’t seen anything that bad – just a tiny bit of fraying along the edges.
I can’t really tell what part of your old blue seat that is in the picture – is that where you peeled it by hand, or did it actually come apart that much from normal use? That would be very odd.
I would cut off that seat attachment point and use a different design… having the cord run through two holes like that will multiply the amount of stress on the fabric, which might be why it peeled so much there. It’s too complicated to describe why without a vector diagram, and I know it’s counter-intuitive, but you’d be better off with just one hole there (or two holes with the same spacing as the holes in the seat, with two separate cords connecting the seat to the packraft, both pulling in the same direction independently of each other).
As an aside, if you attach the seat to the floor instead of to the tube, then if the attachment point fails there’s no chance of it causing a leak in the tube.
I think I should add a video showing my seat attachment point.
I’ll also add a step to the instructions suggesting people apply Aquaseal or Seam Grip+WP over the seam strips and any exposed edges with to prevent fraying and peeling over time.
I think if you coat your seam strips and any other areas of concern with Seam Grip+WP they should hold up fine going forward, but please continue to monitor things and let me know if you see anything else coming apart.