Right now, I have a good variety of shorts, novellas, full-length novels, and extra long novels on my reading devices. I love the variety. Sometimes I just want a story I can finish in a short sitting. I like the satisfaction that comes from finishing a story, and any length story has *some* satisfaction to it (even if it's terrible, then I'm satisfied that I'm done wasting my time).
It's only recently that I've allowed myself to *not* finish books I dislike. With ebooks, I always have another few hundred to choose from, so if I don't like a book, why waste my time? It was a difficult switch in mindset though. I also have trouble *not* eating everything on my plate. Even if I'm not hungry.