Depending on the scope of a project, it can take anywhere from one hour to a couple of organizing sessions to organize a space. In order to keep it organized, you need to work at it. It’s similar to weight loss and exercise. Once you reach your ideal weight, you still need to consciously work at eating right and exercising to maintain that weight. Once you organize a space, you need to actively keep it organized. Research shows that it takes consciously acting on a new behavior for just 15 minutes a day for 21 days could create a habit, to do something “automatically.”
So, whether it is keeping your email in-box organized or keeping your children’s playroom organized, you need to actively do something to maintain it. I’m not a fan of Post-It notes because often it is used along with some other organizing to-do list/app/planner and when you have more than one system in play, things can get lost. In this case of creating new habits, you could write one or two words to remind yourself of the habit you are working to create. Stick the Post-It note somewhere highly visible and make tick marks for 21 days as a visual reminder and self encouragement.