A full charge on the Hushh will last 6+ hours with no night light usage. Please note that the night light uses much more battery power than the sound and that higher volume = faster battery drain.
A full charge on the Rohm will last at least 6+ hours. (This is because Rohm does not feature a night light.) Again, louder volume = more battery drain.
A full charge on the Go will last up to 12+ hours.
It is also possible to run the Hushh, Rohm, and Go while they are plugged in and charging.