I wore all 14 pairs on a rotation for about a year now. I did notice at the 9 to 10 month mark that I had lost so much tread that I DO slip when they are wet. I fell with some on! It was not fun, since I counted on them from keeping me from slipping...
I have found that they get harder to clean, and have little or no tread on all pairs. I still wear them.. well, I will in another month or 2. I also have 3 pair of the Athens flip flop type CROCS. I have worn these for 3 months now and they are still very cushy. The other 14 pair are in various stages of comfort.. mostly still cushy, but the orginal ones I got 17 months ago are not as comfy as the others.
I had a very badly injured left foot, and surgy on my right knee. For a year these are the only shoes I COULD wear! With the extrem swelling on the foot, and the pain in the knee..., well, they helped a ton. I did check with my doctors and 2 out of 3 approved, the other wanted lace up shoes, but I couldn't fit my foot in for over 1/2 of this time! Even my Phy Therpist isn't to against them...
Someone on another post said that they placed them in their dishwasher and forgot to turn off the heated dry... they shrunk. But then another poster said they did the same thing and they stretched out to fit good as new! Might try it as some of them are really stretched out on the left foot and way to big now....