I agree with Mike & baldrick. With time you might find other uses for your Ipod. I use mine for our outdoor deck system, in our cars and lately some of the hotels we've stayed at have had nice Ipod clock radio systems in the room.
As to your original question, one way to solve your problem if your using Windows, is to take your duplicates and put them in a separate folder, create another user on the system and have iTunes for the new user point to the new folder you created.
Len