another hint that can gain a lot...
use CleanManager (start > cleanmgr )
and tag the "remove service pack uninstall" and/or "remove patch uninstall / clean up windows update" (or something like that)
(I think it's a seperate button in Win8.1)
it will remove uninstalls of applied service packs & patches and clean up the mess in the windows\winsxs folder.
the only disadvantage is that you can't uninstall the patches, but clever people disable windows update and run it manually
so it's safe to use this when you didn't notice issues after the last manual update.
I also use this trick to gain thin provisioning space & transfer time when virtualizing servers.
(it requires an additional KB install for that feature on Windows servers tho)