No Fibs — Honest Limitations
Caffeine's half-life averages ~5 hours but ranges widely (~3–7h) by genetics, pregnancy, and smoking — this uses a fixed 5h estimate. "Level at bedtime" is a rough projection, not a sleep guarantee; sensitivity varies too. The curve is a teaching aid, not medical guidance. Cut-off advice (e.g. stop by 2pm) is general, not individual.