answer:No intolerance build up that I know of. Think of all the folks that drink multiple cups a day for the better part of their lives (54% of US adults drink coffee everyday) You can build tolerance to the caffeine over time, and have withdrawals if you don’t get the caffeine at your regular schedule, but that doesn’t sound like what you’re asking. Your “freak out” was because caffeine is a stimulant for your nervous system. So your brain can’t relax with too much caffeine, but the threshold for a permanent effect would be really high. I’d guess you’re just overthinking it. If you want to have some coffee, have some, but leave the 800mg binge alone. Beyond a bit to “wake up”, more isn’t better when you’re talking about stimulating your brain and heart. Put another way, if you’re used to having a drink or two with dinner, then one day “jolt” your system with 7–8 shots in a short time, the feeling is going to be different. More from wikipedia – Health effects of caffeine