I have a laptop that is running Windows 8, and I noticed this issue just recently as a friend of mine was also experiencing it. Upon further investigation, I have come upon a solution that I am going to share with you!
Why Windows 8:
Ok let me get this out of the way.
1. My laptop dual boots to Windows 8 and Backtrack 5
2. As an admin you have to be ahead of the curve, whether its Vista or Windows 8, OSX etc.
That is why... Let us continue.
Why does my Windows 8 Laptop disconnect from WiFi periodically? (This isn't the same as the limited connection problem)
Simple, your power settings tell it to.
As a default setting, when your battery runs low or you are not connected to an outlet your WiFi antenna drops out to conserve power.
So lets amend this problem.
Step 1: Press the "Windows" button aka the "Windows Orb"
This brings up your Windows 8 "Metro Start Menu"
Step 2: Just begin typing "Control Panel"
This will bring up a selection for the control panel, scroll over and open the control panel.
You should now be at your desktop with your control panel open
Step 3: Select "Power Options" under Control Panel
You are now in the power options screen and what is selected by default is the "Balanced" power plan, this is good, leave it.
Step 4: Click on "Change Plan Settings" on by the Balanced Plan.
Now you are in the "Edit Plan Settings" Window.
Step 5: Click on "Change Advanced Power Settings"
The window should look like this; this is the important part.