I recently picked up a used set of Shimano 105 9-speed STI levers. (Yes, my first brifters. I've also never yet used outboard-BB or ISIS/Octalink BB, or threadless headsets, before.) The Craigslist seller said that they had 5-700 miles on them, and they appear to be in good functional shape (with some scratches on the front cap, but mainly cosmetic). They do have some dirt-film on the edges of the levers that don't get touched. Rachet mechanism appears to work fine.
I'm wondering if I should just throw them on a bike and get riding, or if it makes sense to flush them with WD-40 or ProLink or something. Are there easy things I can do that will make the shifting rachet mechanism last longer or work more smoothly? Just trying to collect some data here.