: Often incorrectly mixed batches will cure if given enough time.

Allan,
I might be able to agree with your statement had it been worded a little differently, something like - "sometimes batches end up taking longer to cure than you might have expected". I've had epoxy batches take longer to cure than I thought they should. As I recall from an epoxy demo I saw at a kayak event years ago, the cure doubles every 10ºF drop and halves every 10ºF increase from 77ºF -- temperature & time are definitely factors. However, incorrectly mixed epoxy stays incorrectly mixed no matter how long you might wait. The curing of epoxy is a simple chemical reaction in which the molecules in the hardener react with molecules in the resin in a predetermined ratio. If the hardener/resin are not mixed in the proper ratio, depending on how far off you are, you may end up with epoxy that hardens, but not to it's full strength potential, or you might end up with a mass of soft goo on your kayak. If you are short of one component, you'll end with a corresponding amount of the other component un-reacted in your mix, a problem which time can't fix.
This is an extract from Raka's epoxy manual that emphasized the need to control the mix ratio -- "I want to emphasize the importance of proper mixing. Epoxies strength and desirable properties come from the complete mating of the resin and hardener molecules in the correct ratio. Too little hardener produces brittleness, and too much hardener makes your epoxy softer with the accompanying loss of strength. If you make an error, you're safer to use a little less hardener, than too much. Generally speaking you can have a 20% error tolerance on the minus hardener side and 10% on the plus side and still get an acceptable cure. Regardless, your cure will have less strength than its ultimate potential!"