I drink about a couple of liters per day, sometimes less, depending on the mood. I think I have no caffeine sensitivity at all, since I have normal BP, no sleep problems, and am able to stop drinking all caffeinated beverages for a few weeks without any (obvious) problems (did it several times after getting tired of the taste).

All these personal anecdotes (when I stopped drinking coffee, my wife returned to me, and I won in Powerball!) sound very strange to me.