I think you can go frugaler. Make it 1-ply, cut it into thirds. Should last a month.
This weekend, from the bathroom of a friend of mine, in São Paulo. The light is to illuminate the shower. Just be sure it doesn't... y'know... fall into the shower and break the bulb and... y'know... electrocute you? Y'know?
From the submitter:
I am in IT. Our bathroom light burned out. We have no extras but got a USB light!! Wall power to PSU to motherboard to USB port to USB light! FIXED!
When you've got to s*, it's got to fit!