Well, not really at end game.

Pre-level 50 you don't really have a choice, haha. Energy is a pain then. Post-level 50 it gets worlds better.

At end game, it all depends on the spec and how much you are spamming abilities.

Take assassination for example. You might have 60 energy and you want to cast mutilate, but your bleeds are about to fall off. It might, depending, be better to hold off and wait till you can cast that mutilate and still have the energy left over to refresh Rupture and then Garrote. Or any combination of abilities.

It's why I love the spec. It's very straightforward but with variations from fight to fight depending on positioning, boss mechanics, minimal RNG, etc.