Windows 95 could run for 45 days before crashing. Out of the box, it looks like Windows 8 won't be able to manage that feat, with Patch Tuesdays every month.
90% of the updates I have received haven't required a reboot.
Windows 8 also warns the user on the lock screen during the three days that a reboot is necessary/impending like so http://blogs.msdn.com/cfs-filesystemfile.ashx/__key/communit...
That is a tenuous description of "authorization." The user is asked once when they set up their computer whether automatic updates should be enabled and the downsides are not outlined. It is strongly "recommended."
On the plus side, Windows 8 is handling it much better.
From here http://blogs.msdn.com/b/b8/archive/2011/11/14/minimizing-res...
"WU will consolidate all the restarts in a month, synchronizing with the monthly security release. This means that your PC will only restart when security updates are installed and require a restart. With this improvement, it does not matter when updates that require restarts are released in a month, since these restarts will wait till the security release. Since security updates are released in a single batch on the second Tuesday of every month, you are then getting essentially one restart a month."