[Zak]

> Is this a feedback loop? We keep increasing caffeine content because we need more for our beverages to have the desired effect for customers?

Tolerance, or physical addiction is exactly that. A given dose is less effective after a certain amount of repeated use and a larger dose is required for the same effect. Not using the drug at all may cause withdrawal symptoms.

[Waterluvian]

And now we’re selling a litre of iced coffee in a single serving vessel, which has 396mg of caffeine (or 475mg if you get the extra charged version).