Humm I just upgraded 43 machines over the last two weeks to 8.1 and have yet to see that issue but 8.1 does have a power setting that turns off wifi after it is unused for "x" amount of time.
FYI, Windows 8 has a default feature to turn off the wireless adapter card to save power. To disable it:
Control Panel -> Network and Sharing Center -> Change Adapter Settings
Right click on the connected wifi connection -> properties
Clicks "Configure..." button -> select "Power Management" tab
Uncheck this "Allow the computer to turn off this device to save power"
Ok and restart Windows
After about 20-40 minutes of being online the connection drops and it seems theirs plenty of people explaining the same thing. this has been going on since the 8.1 upgrade from windows 8.. their seems to be many people having the same issue. This needs to be fixed, I'm sure that Microsoft is aware of this issue and is dragging their feet. some forum people explained some sort of advanced way to fix by playing with settings, but we should not be pushed to fooling around with settings and what else. I've come across about 100 people in forums with the problem.
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