That’s not true - the average storage duration for grid batteries used in non-stabalization roles is 4 hours - see https://www.eia.gov/todayinenergy/detail.php?id=51798 and that’s from a few years ago. Since then the xMW, 4xMWh format has become almost universal.
A typical grid-storage battery will have enough storage to dispatch power at 100% of its rated capacity for 4 hours.
Of course if you draw out the energy at less than full capacity, it will take longer to fully discharge.
The largest battery currently in the US - Moss Landing - for example is rated 750 MW/3,000 MWh - which means it can sustain 750MW of output for 4 hours and it does this daily.
