The amount of time it will take for the epoxy to stop smelling will depend on the brand of epoxy you are using and its VOC level. However, the standard rule is that it will stop smelling once it cures completely if you mix the epoxy correctly.  Depending on how thick your epoxy pour was and the temperatures where it is curing, a complete epoxy cure can take from a day to about a week, and after this, the smell will stop being strong. It might take about another month for the scent to completely go away if you were using a very pungent epoxy.