If you are able to age in place and have the assets and finances capable of doing so, paying down the mortgage is a great option in planning for the future.  With the understanding that retirement-income planning is essentially establishing an income stream that can provide for most expenses throughout an individual’s retirement, paying down the mortgage before retirement will lower or eliminate that specific monthly expense.  The question lies in whether it is more cost effective to pay down the mortgage or buy an annuity or equivalent product.  Factors such as the mortgage's interest rate, annuity costs, and liquidity concerns come into play when making this decision.  Ultimately, if the house is underwater, it would be advantageous to pay down the mortgage until it is afloat.  At that point, look into other options such as investments, annuities and other retirement options that can be better than paying off the mortgage in one foul swoop.