I've gotten a lot better. I'm down to usually 1/2 to a full 16oz rockstar per day (eq to about 2-4 shots of espresso or so). Though some days I'll get a venti starbucks iced doubleshot (6 shots of espresso over ice with choice of milky product over it) in addition to the regular.
My highest amount I think was something along the lines of 2g of caffeine over the course of a day via beverages. 2 or 3 24oz rockstars and a few starbucks things.
One shell station near a place I worked had "wild buzz" energy drink in the soda fountain.
That was great. effectively a 44 or 60oz redbull for under $2. Didn't last long though.