Well you could define life=heaven and death=hell, but it’d be sort of a redundant addition to what we already mean by life and death. There doesn’t have to be a heaven/hell that really exists, the words can just refer to the ideas as normally expressed (and it’s probably clearer and easier to stick to those older definitions).

Besides that, non-existence wouldn’t really be hell because it wouldn’t be bad. Or good. Or anything. You’d have no experience of anything – no pain, no suffering, no mental anguish at the existential dilemma of the human condition. Also no pleasure or joy or … anything.

Life, for all it’s wonderful attributes, I wouldn’t precisely call heaven either. After all, it does also include the potential for a lot of unpleasant experiences (ones that I’m thankfully, for the most part, spared from living through)