I decided to replace the pdms in my 3d printers vat not because it had begun to start sticking but because it was the same ratty pdms layer that prompted me to try the pressure vat refresh method in the first place. I made the new pdms layer thicker, about 3.5mm, my rationale being that you could diffuse more oxygen into the top layer of the pdms using pressure without diffusing the oxygen so far into the pdms that it will outgas out of the bottom and cause bubbles to form between the pdms and the glass vat floor window. So far everything seems to be working well, I have printed over 1000 layers so far in 2 print runs pressurizing the vat to 20 pounds of pressure for 5 minutes before each run (I am beginning to think that using a reletively low pressure and adusting the time the vat is under pressure is the best way to adjust the diffusion rate).
The type of 3d models I was printing insured that I would be printing flat layers that covered most of the live print area on my build plate (130mm X 73mm @ 67.7 microns X/Y, 75 microns Z, 1080 X 1920 projector) in addition to a “bed of nails” set of supports (which are notorious for fogging pdms). Because of the design of my printer I can tell a lot about how well things are printing from the sounds it makes and how it moves. I was getting smooth “vacuum release” type vat tilts for layers that were large flats or presented large closed “suction cup” type profiles, other layer exposures like small flats or small open or closed profiles did not give any signs of being released at all, also, none of the layer exposures showed any signs of resin sticking to the pdms when the vat tilted and, at this point, there are no signs of the pdms fogging. A note: I have started using Dawn dishwashing liquid (the Swiss army knife of dishwashing liquids) water and a microfiber “washcloth” to clean my vat and the pdms vat floor, it works a lot better than alcohol for Makerjuice SubG+ and you clean the vat like you would a dish.