figure 1: We only start working harder when the pressure
of the delivery date is near. Usually we are late.

figure 2: To overcome the late delivery problem, a smart
project manager sells his team an earlier delivery date.
Even smarter developers soon will know, and ignore it.

figure 3: The solution: choose short, realistic "delivery dates".
Satisfaction, motivation, fast feedback.

Why should we use short cycles?

Actually, few people take planned dates seriously. As long as the end date of a project is far in the future (figure 1), we don't feel any pressure and work leisurely, discuss interesting things, meet, drink coffee, ... (How many days before your last exam did you really start working...?). So at the start of the project we work relatively slowly. When the pressure of the finish date becomes tangible, we start working harder, stressing a bit, making errors causing delays, causing even more stress. The result: we do not finish in time.

We know all the excuses which caused us to be late. Of course it's never our own fault.
It'is not wrong or right. It's human behaviour. It is how we function. So don't fight it (we cannot fight our genes) but also don't ignore it. Accept it and then think what we still can do.

Smart project managers tell their team an earlier date (figure 2). If they do this cleverly, the result may be just in time for the real date. The problem is that they can do this only once or twice. The team members soon will discover that the end date was not really hard and they will lose faith in milestone dates. This is even worse.

The solution for coping with these facts of human behaviour is to plan in very short increments (figure 3).
The duration of these increments should be such that:

When I was thinking about these issues, I thought: "Three weeks is too long: people will not work really focused the first day" and "One week may be felt as too short for finishing real tasks; people will probably not accept it". So I decided to start with 2-week cycles.

The experience in an actual project, where we got only six weeks to finish completely made us decide to using one-week cycles. If you cannot even plan a one-week period, how could you plan longer periods ...? The results were such, that we will continue using one-week cycles on all subsequent projects.

Note that the pressure in this scheme is much healthier than the real stress and failure at the end of a Big Bang project (delivery at once at the end). No stress, however, is boring. Good stress (level of figure 3) gives people the feeling of accomplishment and is sustainable over many cycles. Bad stress (as in figures 1 and 2) makes us inject too many defects and is bad for our health.