How do you know when your SLA resin tray needs to be replaced? How do you know when your SLA print tray has lost its non-stick coating?  


Are there visible or testable signs you can use to determine it is time to invest in a new resin tray?   
Is it best to count prints and estimate?
Once the non stick coating wears off you'll notice degraded print quality over time and a more agressive sound from the print breaking free when switching layers as the print uses more and more force to break free from the tray with each layer when the non stick coating degrades. The good thing is this will not happen at once so you will start to notice telltale signs previously and you can lessen the wear at specific points of the non stick coating by using different parts of the build platform instead of printing exactly in the center each time.