These estimators don't exist. Such a reliable estimator has more incentive to use his ability to estimate tech stock prices and become rich rather then work for you.
In fact hearing this line, no one will work for you. Frame it and make it your motto, see what happens.
They sort of do though. As hyperpallium alluded to above, the trick is to vastly overestimate the time required, then let Parkinson's law take up the slack.
In fact hearing this line, no one will work for you. Frame it and make it your motto, see what happens.