Once upon a time, to-do lists were simply scrawled on scraps of paper. These days, the exploding number of productivity apps means that not only can people upgrade their lists–we’re also discovering new information about the way people actually work.

For instance, what happens when somebody puts an item on a “someday” list? What happens to it?

Recently, the team at Any.do, a productivity app that lets you assign tasks to Today, Tomorrow, Upcoming, and Someday lists, decided to find out. They analyzed a select group of highly productive folks who logged in daily, entered action-oriented tasks, and got at least 75% of their tasks done each day. (That’s a much higher completion rate than the average person, Any.do reports).

The “Someday” list items, says founder Omer Perchik, ran the gamut from planning a trip to Japan to fixing the kitchen sink. “They can be tasks with many steps that require lots of planning, or simple tasks that are easy to put off,” says Perchik. “However, they tend to be less immediate items.” One of the most common tasks on Any.do is “call mom,” but that is usually in the “Today” bucket, not the “Someday” bucket.

Regardless of the task, though, Any.do discovered that if a “Someday” task hadn’t been moved up to a Today, Tomorrow, or Upcoming list within six weeks, the probability of it ever happening dropped off drastically.

What’s so special about six weeks? Says Perchik:

We think six weeks is the window where people are the most enthusiastic about doing something. The sense of novelty and excitement are great catalysts for getting things done. Planning a trip or fixing something around the house might be projects you feel up to today, but after six weeks they may have lost their original luster.

That realization can provide you with valuable insight. “Once the initial inspiration has had a chance to wear off, you’re left with your true intentions and that can be a very powerful piece of information,” says Perchik. In other words, if you put “take skiing lessons” on your Someday list, and six weeks later you still haven’t researched the lessons (much less signed up for them), that’s a good sign that skiing isn’t a big priority in your life right now.