Maybe libraries should issue subtle notifications when patrons check out books multiple times. Something like, "Last borrowed November 2016." Nothing as overt as, "Are you completely unaware of the fact that you've already checked this book out, plus renewed it, so there's a good chance you've read it before?!"
I suppose this falls into the category of the"smart" features I often decry. How many times have I joked that I don't want my TV or refrigerator to be smarter than I am? So why should my library be?
Which means ... I'm back to relying on good, old-fashioned, oh-so-fallible human memory.