It always takes longer than you expect, even when you take Hofstadter's Law into account.
Hofstadter's 1979 law is self-referential by design, which is the point — building in a buffer does not help, because the estimate of the buffer is subject to the same law.
In practice
- A team that added a 30% buffer to a six-month estimate delivers in eleven months.
- A move scheduled for a weekend with a day spare takes the following week off as well.
- Further reading
- Wikipedia
- Subject
- Decision-making & Reasoning
- Essay
- Paradoxes that broke theories, and sayings that outlived them