While Vladimir and Estragon wait for Godot, they also wait for nightfall. For some reason (again, arbitrary and uncertain), they don’t have to wait for him once the night has fallen. The classic interpretation is that night = dark = death. The falling of night is as much a reprieve from daily suffering as death is from the suffering of a lifetime.
There’s also the issue of the moon, as its appearance in the sky is the real signal that night has come and the men can stop waiting for Godot. Estragon, in one of his "wicked smart" moments, comments the moon is "pale for weariness […] of climbing heaven and gazing on the likes of us." Though the man remembers nothing of yesterday, he does in this moment seem to comprehend the endless repetition of his life. And if the moon is weary just from watching, imagine what that says about the predicament of the men themselves.