Bump as a reminder...At 12K mine was fairly dirty. Being fiscally conservative (cheap) I just rinsed mine out with sprayed hot water and figure I can get 2 or 3 washes before replacing. The backing membrane seems to be plastic.
2012 JKU Rubicon -Natural green pearlcoat
I replaced mine after 15K miles and it was actually in pretty good shape minus lots of dead bugs. What a great way to go though if your a bug...you get to catch a ride on a Jeep through the woods for your last hurrah!