I have some brass thats been reloaded either 8 or 9 times and isnt having any problem . I havent washed or tumbled it and all seems to still have the poly coating intact. I use the hornady lube you rub on with your fingers thats mostly lanolin , I was afraid the oil based lubes might soften the coating .
I did want to point out that the all my reloads are light enough that I am getting fowling back on most of the case indicating that my cases are not fully expanding to fill the camber so the poly coating present or not really wont make any difference . The point of the coating is to allow the bolt to start opening while there is considerable chamber pressure present so I guess if your running full bore loads you will start to see some extraction issues as the poly coating wears