If left on continuously, with good fully charged NiMH batteries, the flowlight will last 3-4 hours on "bold" mode and 7-8 hours on other modes. With rechargeable lithium-ion batteries, flowlights will last 10 hours or more. If you are in superbright modes, your light will last about half as long.
Spectrum lights: Bold, Bliss & Breathe are very power hungry settings
Other colors: Bold is the most power hungry.
You can find rechargeable NiMH AAA batteries on our website here: http://www.flowtoys.com/powerup/batteries/
If you have any questions, please feel free to contact us!