Mortgages

Please answer the following in at least 200 words:

The most common question I get as an advice columnist is, "Should I prepay my mortgage?"

Additional principal payments on a mortgage shorten its effective life and reduce the total interest expense but often come at a price, the inability to invest for retirement and other long term financial goals.  How would you prioritize these conflicting goals?

Seniors often want to raid their retirement savings to pay off the mortgage.  What are the pros and cons of taking that step?