Microsoft today reminded customers that the Windows 8.1 Preview will conk out on Jan.15. "Now that Windows 8.1 and Windows RT 8.1 have been generally available for a while, it's time to get all your remaining devices that are still running Windows 8.1 Preview or Windows RT 8.1 Preview to the final GA release before the Preview release expires," Microsoft said in a short post to a company blog Wednesday.