Faster cure also can heat up tremendously if done in large batches. If you mix up a total of 1 oz 5 min epoxy and let it sit in the container where it was mixed... it will start to fume (smoke) within 1 min. It can start to harden in under 2 min.(because heat speeds the curing) It is possible for it to ignite a styro mixing cup. The fumes can be lethal.

Longer cure time epoxy tends to be thinner. making it easier to avoid applying excess, but making gap filling more difficult.