Notice that I didn't say "relisting." If you don't already know this tip, it can be helpful to use the "sell similar" option rather than the "relist" option when one of your listings expires and you want to put the item back on eBay. The difference is that eBay's search engine will treat a "sell similar" listing as a new listing, so you get a little boost (or so I've heard!) in the search algorithm as your item will appear as "newly listed." If you just "relist" the item, you don't get that boost.
Different people say different things, but in the reading I've done on Facebook groups and blogs authored by eBay sellers, many people insist that you need to keep your eBay profile active by having newly listed items all the time as this is supposed to help you in search results when buyers are looking for items.
And I can say from personal experience that within 24 hours after relisting it, I sometimes will sell an item that had previously been sitting around with no attention from buyers. It happened just this week with a pair of new-with-tags Alfred Dunner pants I'd found at the Goodwill Outlet, and it happened a couple weeks ago with this cool Freddie Mercury tee.
I've been so busy that I haven't had the chance to create new listings, but "selling similar" has kept me going with some sales here and there. Hopefully I will get a bunch more listings done soon as I'm going to submit my spring quarter grades in a few days. I need a break from my day job to get back to eBaying!