The graph titled "Caffeine Accumulation With Long Half Life" is weird. Isn't that not how half-life works? A higher blood level should mean faster elimination, but here it acts like the baseline changes each day. No matter how slow the user's clearance is, the ratio should always take the same time to get halved.

Edit: actually this graph implies that people like the author would end up poisoned by a lethal dose of caffeine after a few weeks to months. Maybe these people exist but it can't be common.