the most genuine answer that i can give is that assuming eternalness exists, then we are all one, and we are all in heaven and hell at both the same time and neither at all.
YOU REALLY NEED TO THINK ABOUT THIS!!!
Eternity, infinite span of time, endless "endlessness".
In that scope, it takes only one being. that being is all of us combined.
really, the notion is preposterous. either there is no ultimate punishment, or the complete whole of reality is finite, and not eternal.