Get the update from Microsoft here. (updated with Update 4 link)
Save the file to a folder.
open the folder
Pro tip – Shift + right-click the background of the folder and choose ‘Open command window here’
in the command window type VS2013.4.exe /Layout
(or VS2013.1.exe /Layout or VS2013.2.exe /Layout depending on your update)
It will then ask you where you would like to save and extract the files.
This step will take some time depending on your download speed. This is the step that adds time to the install when you choose the web installer.
You will now see a folder with the update installer along with all the source files. You can now store this safe on a network share or your hard drive and update your installation of Visual Studio without downloading 2GB of files!
This should work for any version of Visual Studio going forward.