According to the folks that make the epoxy that I use for bedding, there is no shelf life. The only thing that will happen is that the resin or the hardener may change color over time (to amber). This does not affect the finished product strength, only the appearance. While on the topic, if anyone wants to color their epoxy I recommend tempera paint powder (the same stuff you used in primary school) available at art stores. The powder is made from natural minerals. Equal parts of red, yellow and blue well-mixed into the resin before the hardener is added will give a nice dark brown color. Want the mix a little redder add a bit more red. Same with blonde, add a bit more yellow. For a 2 oz combined mix I use 1/4 tsp of each to start. For a release agent I am using a product that many marine builders use called Meguiar's Mirror Glaze Maximum Mold Release Wax @ $14.95 per 11 oz can. I buy my epoxy materials and this wax from a marine supplier. A single can lasts a long, long time, like several years.