The DVDs have *tons* of small files for all the individual language support, and will indeed take forever to file copy.
The only way to speed it up is to specifically copy over only those languages you plan to install. You will find these on each DVD under the Localize folder.
But honestly you may not want to do this file copy ahead of time, as you are seeing of course it does not save much time, rather it greatly increases the time. Also, you will end up with a somewhat more fragmented hard disk than you would have otherwise at the end of the install.
