Regardless of your need for duplicates, consider your answer to this much different question:
If your computer were stolen, how difficult would it be for you to live without the data on it?
Do you have years of bank records, email, poetry, academic papers, photos, movies, and so on stored on your computer? If so, chances are your answer is "extremely difficult." On the other hand, if you use your computer only for casual Web surfing, playing games, and listening to music, living without the data on your computer may be little more than a minor inconvenience.
Although a duplicate includes a copy of your data, an archive includes many different versions of your data, making it much more likely that you'll be able to retrieve the information you need in the event of a problem.
The greater the amount of personal data on your computerand its importance to youthe greater your need to maintain archives (for more info, see The Archive, page 94).
Though there may be some exceptions, the ideal backup strategy for most people consists of both duplicates and archives. I discuss each of these in the pages that follow.