I don't think energy is the limiting factor here. A better analogy would be with the limits of computability. Garbage collection tasks are postposed to when we're asleep, but they can only be put off for so long and there's a capacity for "stuff to consolidate later" that fills up.

Something that you probably could get is a nob to control the adaptability/efficiency setting on your brain. At the cast of learning/remembering nothing, you could "execute" for longer. We know that real brains make this trade off, but the transition from one mode to the other is slow because it's reactive.