I've just been deleting them, but I don't make the same item twice (except for a couple of hand forged simple wire earrings that I sell on another site, everything I make is one of a kind).
I used to keep some items showing as 'Sold', for awhile, on another site where I sell my jewelry, and I've found that most often than not, buyers wanted a copy of a design I had already sold and I didn't have enough or all of the components to make it and it would be a good 3 weeks turnaround time for me to receive the parts and make a piece fairly similar, that often, they didn't want to wait that long, and often, they didn't want a similar design, they wanted the exact same item, which is often hard to do (using gemstones and/or lampwork beads, as the beads are all unique in some way or I was unable to find the same shape or same color)...
As much as I like to show my past work, I find that it backfires, so now I list what I currently have for sale, if they want something, they can choose amongst my available pieces or I can design something entirely customized for them, a brand new design.
This is my own experience, others may have a different point of view.
I hope this helps,
Cheers,
Nathalie