You don't have to keep your HMD in the dark you fucking retards, just don't expose the LENSES to SUNLIGHT for any extended periods. An extended period would probably be while you aren't using it. 

SUNLIGHT contains a lot of INFRARED and ULTRAVIOLET wavelength light, which cause heating far more than the visible wavelengths of light do. Your room lighting isn't going to kill your HMD, nor is reflected light from a nearby surface because the IR radiation has already been absorbed by striking the first surface. 

DIRECT SUNLIGHT ONTO THE LENSES IS NO. 

You don't have to hide it in a fucking box in a cupboard jesus fucking christ what do they teach you in schools these days.