The trend towards shorter iterations, while being a good demonstrator of increasing development capability, also tends to rob planners of an opportunity to step back from project minutiae.
I’ve noticed a pattern in which people regularly over-commit to work and consequently regularly under-deliver, and don’t seem able to break the cycle. In fact, their actions seem to perpetuate the cycle.
When you estimate how long something will take, about half the time it should be done early or on time. Almost anyone reading this will know things are rarely done sooner than expected, especially if they’re difficult. People have been shown experimentally to be poor estimators, with a marked bias towards underestimation of time required to complete tasks.