These Voice Memos really need to be short for them to work in the iPhone environment. You can make them longer, but they end up being fairly useless. These are supposed to be short notes that you can reference easily, and if you record long audio pieces, you are not going to be able to use them for information. The best way to do this is to constantly update your collection of Voice Memos and do not keep them on there for too long. The best way to do that is too keep a weekly log.