I talked to an epoxy expert once (works for an epoxy company in Bay City MI) and he said the bottom line is quality. He said all epoxy will go bad over time (usually it is the resin which will harden on it's own) but how fast it becomes junk is based on quality. I've had some problems with Tower Hobbies 30 minute and 5 minute going bad in a matter of a couple of short months. Careful when changing brands because a different label does not always mean a different product. Just my usual 2 cents.