I honestly believe its a factory thing. I have had units that NEVER shed. and i mean never. My famous partial thats god knows how many years old, still has not shed lol. and another unit i have that I got in 2005 has not shed either. Then i got some new units that shed in 3 weeks. and it is nothing i did differently. I think it depends on what worker u get at the time and how good they tie the knots. I mean there in the business of producing volume. I wouldnt be surprised if the factories make sure the knots aren't too sturdy.