I used to buy smooth On in quart cans, and it does have a shelf life. Mine went bad after 5 years, and it failed on glue ups. Threw it away. Best to buy it in pint cans ,and use it up in a couple of years for limb lams ,handles, and tip over lays. I have used knox gelatin, and tb 3 for sinew backing, and tb 3 for applying snake skins. Both work, so it is just a personal choice. Most on here prefer hide glue for sinew backing, and claim that it makes a snappier bow. Threw a chrony I didn't see that much difference to even worry about it.