Actually, the metaphor is pretty good, except they missed a key change: in real life if the &quot;test painting&quot; shows you need to &quot;prime first&quot; you now have no idea how long it will take without starting the estimation process all over again.<p>So, in real life, paint the room is &quot;2 days or, if the test painting goes badly on day one, I&#x27;m not sure and won&#x27;t know until the end of day 1&quot;.  And people don&#x27;t like those kinds of estimates.