How long do dark slides last under "normal" use before they need to be replaced? I know this is a subjective question but this thread got me into thinking about when I will need tp replace mine. I bought 5 new 8x10 Fidelity Elite holders back in 2011 and 5 new Toyo 8x10 holders in 2014. I'm careful when using them and store all 10 in a padded film holder case when not in use. New Fidelity replacement dark slides haven't been available for a while and I just checked the B&H website and the Toyo 8x10 dark slide is marked as discontinued.

Thomas