If I'm interested in a book I place a library hold on it or buy it right then and there. I don't keep a TBR, and as far as I can tell people who do don't actually use them (I don't know what people actually do with them, but they often have more books on them than a person is realistically going to read in a lifetime). Basically, for me there's no such thing as a book I might want to read one day, it's either I want to read it now/when it comes in at the library, or I don't want to read it.