Almost every project runs into unexpected delays. A dedicated buffer week absorbs those delays without pushing your final deadline, which is far less stressful than scrambling at the end.
Combine smaller milestones into the same week, or extend the deadline. Cramming too many milestones per week usually causes silent slippage rather than real progress.
Schedule it as early as possible in the timeline and follow up proactively rather than waiting until its scheduled week to check status.