I had a bit of a sealing emergency today and the only thing I had on hand was a tube of 100% silicon that had an expiration date of 2017. It's been in my basement the entire time (our basement is a steady 65-70 degrees year round). It was stored nozzle down. When I spiked it I got a bunch of liquid but then got the silicon as I squeezed. It seemed a bit runny but I used it anyway and 30 min later it's set just like it should be. My guess is some of the solvent came out of solution and migrated to the bottom of the tube. Other wise it seems OK, other than being a bit runny. I expect the end of the tube is probably really thick. So I think at least with silicon it's OK to ignore that expiration date. Gonna go dig in my electrical drawer for a blue wire nut now.
