I'm investigating this very question myself. I think it's probably something each person has to figure out for themselves. Anecdotally, the mathematician Paul Erdos took amphetamine (not coffee but same idea) every day and considered it crucial to his work. Also, I've been trying drinking only small amounts of coffee: 10g beans + 160g water that I make myself every morning with pour over. And it's great! I can definitely feel it, but I don't get jittery/anxious/unable to focus like I used to gulping down big cups of coffee.