I've only got one face, so I only need one of each razor.
While my collection contains several duplicates and triplicates, its been because I have bought bundled sales, and coming up with more than one of the same item is unavoidable. It provides me with a lot of extra stuff to put back in the market.
The one exception to this is my Birthday Razor (Z-3) ... I only have one example right now, but I bid on every one I see, and it wouldn't bother me if I wound up with a dozen or more of the same exact razor.