One of the things that religion promises you is infinite life. Humans often have a tendency to fear death, and religion uses this. Throughout all religions they tell you that after life you go somewhere else, whether it be Heaven, Hell, the Underworld, Asgard, or any other place, but some religions become so focused on the afterlife that they are practically worshiping death. And if all you are doing is focusing on the next life (if it even exists) then you are not focusing on this life.
Some people say that it must be depressing thinking that this is it, and when you die there is nothing. But that is not the case, we do not live for death, a finite life makes living more valuable. If you only have one life then it encourages you to make it worthwhile. No point wasting this life in hope for the next, and it takes the pressure off of you not to be burnt for eternity, which seems completely unjust and illogical.
Everything we are is controlled by brain chemicals; chemicals and electrical signals make us who we are, and there is no evidence that a soul even exists. And if life is infinite, it would turn into a hell pretty quickly. Given an eternity everything that can be accomplished will be accomplished, everything you could possibly do and experience will be, and then you’ll be left for an infinite amount of time with nothing new to do or experience. Everything will become boring and dull sooner or later. After everything is done then there will be only pointless existence.
In a way, people have been dead for billions and billions of years, and if life is finite they will go back to not existing after death. But our bodies will decompose and be cycled back into the universe.