Highlight from 'The Principles of Product Development Flow' by Donald G Reinertsen

A granular timeline subdivides time intervals into very small buckets. When we do this, the coefficient of variation for each of these buckets becomes very high. This makes variance very high and conformance unlikely. Even worse, if we incentivize conformance, people will insert contingency reserves to prevent their tasks from missing the schedule. The more granular the schedule, the larger the schedule reserves. And these reserves aggregate into even longer timelines. The more we increase planning detail and the harder we try to incentivize performance, the worse our problem becomes.