Why should not be left ON WI-FI overnight

In a sea of useful tips on the use of smart phones, one in particular stands out and everyone would be the most serious "taken into consideration". What is it?

How many times have you asked yourself whether your users need to "keep connected" during the night, when you sleep? And the reason that you should not do is so logical. Experts warn that you should not do because of a battery that wifi so unnecessarily exhausts and applied her permanent damage. A similar problem can have and because of included Bluetooth. So leaving precious 'percentages' batteries without any need.