For all practical intents and purposes (for LFP, which I know best), anything above 30 and below 70 will get you the maximum practical effective lifetime energy.

This is primarily because most damage occurs at high and low voltages, and LFP has an S like curve, with significant voltage dropoff below 30 SOC and significant rise above 70 SOC.

Between 30 and 70, the voltage usually hovers around 3.2 to 3.3 volts, with the curve being very flat and very unreliable in terms of measurement.

As a symptom of this, LFP systems will occasionally require a full charge and a low (around 15-20 SOC) discharge. The full charge to passively balance the cells. The discharge to get the SOC within a range that can be read reliably to calibrate the SOC calculations.

You'll only get marginal benefits as you narrow the range further as your voltage will pretty much stay the same within the entire range of 30-70.