If I take a day off I may have coffee or an energy drink to keep me focused. However the norm is for me to have a green and black tea combo before morning cardio on the way to work (US Army) which wakes me up. I would drin more coffee, except that I tae about 400mg of caffeine every day before the gym and I want to keep it healthy.
To help with any concerns however I haven't found a single study that argues effectively against it, only proving its benefits. Not to mention many I know that have drank many cups a day for over 30 years and are probably healthier for it.
-Paul