When working on Final Cut Pro, is it better to (when using an external HD) to keep everything on the HD?

to be more precise, i have footage from a P2 card on my Hard drive that i brought home to edit, and would like to be able to bring back and forth from the studio to my house. should i just keep EVERYTHING on the external? i was thinking it would be better to drag the contents onto the internal for faster access, and then save the project files on the external, but im not sure if the capture changes the files so that if i go back to the studio it wont have the clips it needs.