For example if I put in my current savings, portfolio value and Income data - I derive at 7 more years until retirement. However, given my assets are in a 401k they cannot be touched without penalty until the year in which I turn 55. So, being 35 yrs old - 42yrs old is not a viable option unless it can account for tax deferred and taxable account portfolios separately. I would think this would be the case for most Americans saving in a 401k or tax advantaged retirement account. It would be great if the IRS rules could be accounted for with the model.