The recommended Depth of Discharge (DoD) of lithium batteries is 80%, meaning the State of Charge (SoC) should not drop below 20%… if you want to maximize battery life try to start recharging BEFORE or AT 20%, not less than 20%. That’s all.
more: https://batteryuniversity.com/article/bu-808-how-to-prolong-lithium-based-batteries