Thomas Barwick/DigitalVision via Getty ImagesIt really depends on each individual situation (e.g., size of the accumulated asset pool, tolerance and appetite for risk, dependency on portfolio income etc.), but the most common objective of having a retirement portfolio is to cover a notable portion of living expenses over the whole duration of retirement. To achieve this objective, obviously, the portfolio size has to be large enough just to make the math work. On top of this, the portfolio has to embody ...