The way I see it, and I'm a newbie, there are two facets to this little endeavour. The first is to help prep you for nano. The better you know your characters, their flaws, their goals, their story arc, the easier it is to craft 1600-3000 words everyday. But there is a subtler message in all of this. You are doing something writing related, every day. Turning it from a frequent task into a job. Preparing yourself. Most novelists I've met, at least when drafting, focus most on writing every day, muse or no. You are setting aside your daily time to craft a story. You are making writing a priority. 30 minutes devoted daily to something you love is a day well spent, because you made the effort to fit it in. Even if the exercises are similar, there stands something to be gained from every interaction with your characters. Use it as an opportunity to learn more about them. Use it to think about your setting, and everything else that is happening in their world, from and earthquake in China to an abundance or deficiency in corn crops. Forget the diamonds, and instead concentrate on every facet.