If you are anything like me, you usually have a lot of crap going on your desktop at once.
You know - you are working on something, and then you stop for lunch. Reading the news or whatever, you find something that you want to explore, so you open up a new Firefox window for that. After lunch, it's back to work, but you leave the extra FF window open so you can go back to it later.
Then you come back the next day and Microsoft has pushed out an update that restarted your computer in the night. Bye, bye, all your stuff, you have to go find it all again.
Yes, OK, I know why they do it. Doesn't stop it from being a PITA.
Yes, you can re-set Windows to try and update during daytime hours. Doesn't really help that you will probably get endless pop-ups telling you to reboot RIGHT NOW, while you are trying to get crap done.
Fortunately, Jon Galloway has written up a little tutorial on how to stop Windows from rebooting after each update. There are at least two ways, but his preferred method is to use the settings provided in the Windows Group Policy, rather than registry hacks.
This obviously implies that any updates will not be fully implemented until you reboot your machine manually. Even people with the hottest possible hardware have to reboot sometime, so this will probably happen more often than Microsoft will push out updates.
Jon does note that there have been cases where Windows ignored the settings, and rebooted anyway. Nothing's perfect.
If this is a bit too radical, then maybe it's enough to know that Microsoft has "Patch Tuesday" on the second Tuesday of every month. Most Windows users will see the update appear Tuesday night or Wednesday morning. Just remember to close / save / bookmark stuff on those days, and you will probably be OK.