In the beginning of Avengers: Endgame,
Thanos destroyed all of the Infinity Stones.
But, why did he do that?
Thanos had wiped out half of the universe's population, but given the population of living beings can grow exponentially, why did he think that his job was done?
In optimum conditions on a Petri dish, E. Coli bacteria colonies can double every 20 minutes. Most bacteria colonies double within a week on Petri dishes. With this analogy, the universe population can grow back to previous state within blink of cosmic time scale.
Given Thanos was highly knowledgeable and far-sighted, why didn't he keep Infinity Stones around to do the snapping again?