As weird as it sounds, imagine actually existing forever in a way that keeps accumulating memories, experiences, and from the accumulation, redundancy, boredom, and ennui. Imagine the slow inevitable change of anything like heaven becoming more and more of its own hell on the relentless stretch into infinity.
An end point gives substance to the time before that end point, and even the end isn't truly an end because your matter and energy remain a part of the cosmos.