"There are several reasons you may want to create a
local repository. The first is that you want to save on bandwidth
if you have multiple Ubuntu machines to update.
"For example if you had 25 Ubuntu machines that all needed
updating at least once a week, you would significantly save
bandwidth because you could do all but the repository locally. Most
organizations have decent bandwidth for their network gateways but
this bandwidth is a precious commodity that needs to be used
wisely. Many organizations still have routers with 10MB or 100MB
limits at the gateway but 1 GB network connections internally so
bandwidth could be better used internally. The second reason for
creating your own repository is that you can control what
applications are loaded on your internal Ubuntu machines.
"You can remove any applications your organization does not want
to use on the local network from the repository that updates the
machines. Even better, you can create a test box and test
applications and versions before you allow them to roll out into
your network assuring security and stability."