That can has been nursing me along for years now. About 10 or so. There are companies around here that make drones for the military and they are constructed using composite methods. Much like any company, they have a quality control system that regulates expiration of their materials. The epoxy and hardener are one of such things. The resin and hardener were going to be simply thrown away! Still perfectly good for my use. Normally the epoxy (Fibre Glast 2000) gallon is $130 and the 2060 quart of hardener is $50. Considering how long I've been using it, paying $180 + shipping is a worthwhile investment.
I'll say it again since we are on the topic. The epoxy itself has a tendency to separate over time and become cloudy. The vast majority of hobbyist will throw it away at that point. The advantage of having such a large quantity is that it comes in a metal can and then you can heat it over the stove while mixing and the cloudiness will go away. I've done that at least a half a dozen or so times to my can.