This has come up a few times in different guises. I tested low and high tt attachments and found no discernible difference in their performance. As far as weapons themselves go, the way i clear up this one (of many) of
MA's little misleading statements to my satisfaction is to consider how negatively such a mechanism would affect melee users vs. firearm users. Melee users are going to typically break one or more weapons every single hunt, while firearms need not get below 50% condition at any time. If the statement was taken at face value, it would be very unbalanced in practice.
The statement can be explained by the observation that a weapon at 3% becomes broken, whereupon its performance is (infinitely) impaired...
I notice a decrease in hit rate over time in long hunts myself, as Red mentioned, both subjectively and when i use a tool to measure actual hits. It has nothing to do with the (almost insignificant) decrease in condition of my weapons and a whole lot to do with my own waning attention and sharpness: i sometimes repair the weapon mid-hunt with the same results.