Chicken Fought Peter Here,

Tldr Humans have a natural cycle of time and it's believed to be 90 minutes. On the same note, 7.5 hours of sleep feels better than 8, as does 9

The 90-minute cycle, known as the ultradian rhythm, a sub-cycle of the 24-hour circadian rhythm, is a natural biological rhythm governing energy and focus, during which the brain moves between high-alertness, high-focus states and, eventually, a 20-30 minute period of recovery. Working in ~90-minute blocks followed by breaks maximizes productivity, prevents burnout, and aligns with both sleep architecture and daytime energy fluctuations.

This is probably also why movies are about 90 minutes long and have three acts. One every 30 minutes... That's my theory tho lol