As a matter of course, one of the techs here started copying the i386 folder from the installation disc to the PC hard drive on every PC he set up. I didn’t stop him, because I saw it to be useful when we later needed to add a feature that wasn’t installed in the initial setup (useful=we didn’t have to go pull the disc from our storage).
Should you copy it? That’s up to you. It may only come in handy if you tend to come back later to install things again and again. If you do all of your initial setup all at one time, then you may never really need to have these files stored locally.
Then again, I haven’t tested using a local set of installation files in 2003 <b>R2</b>, but I find it unlikely that it has diverged too far from what I’ve known.