Evolution on earth is heavily influenced on dark/light cycles through its entire history. No evolutionary path that has received this influence can tell us anything about what would happen, on things that are highly correlated to it, for one that has never received this influence.

It's tough to say, there is more than one purpose for sleep, and it may have served other purposes in the evolutionary history that no longer benefit all organisms. For example, humans no longer need to be safely holed up while predators roam the Savannah at night.

It's also hard to know of the infinitely many evolutionary twists and turns lifeforms in the Universe may take, how many of those pathways involve something like sleep - especially on planets without a diurnal cycle.

Anything and everything is a wild guess based on a sample of one where extraterrestrial life is concerned.