As I understand it the body pretty quickly gets used to caffeine use, then taking your typical amount just gets you to the same level you'd always be if you never had caffeine. I still drink coffee though.
I tend to see caffeine as in the long run mostly be useful to let you choose when you're alert rather than increasing total amount of time I'm alert. That can be useful if you get into a good groove of taking caffeine at the right time relative to when you need/want to be alert, but only if you're also disciplined about not taking it all the time.