I fear DeMarco has an uphill battle convincing modern corporations that deliberately planned slack is a good thing. But the typical working day is filled with Q3 activities. But nobody champions the Q2 activities of planning, thinking and analyzing, since such activities appear to be idle time and are often frowned upon. IT project teams often have a similar work environment, and managers can help by teaching team members to differentiate between urgency and importance. I keep four folders in my e-mail program, labeled Q1 to Q4.
Managers can also help team members learn to plan their week in advance.
Ideally, we would follow DeMarco's advice and schedule some slack time during the week. We might even encourage team members to schedule time to put their feet up on the desk and think about what they're doing. But if nothing else, we can encourage our developers to ensure that Q2 items are consciously allocated the time they need, rather than being pushed aside by the immediate pressure of a Q3 interruption.