3. Cash flow matching
If your goal is to retire in 20 years, consider refinancing into a 20-year mortgage. Payments will probably be higher, but most of the additional monthly tab goes straight to reducing principal. At retirement: No more mortgage draining that precious retirement cash flow.
If you are in retirement and need to conserve cash flow, then consider extending the mortgage terms. By refinancing into a 30-year, or even a 40-year mortgage, your monthly payments could drop considerable providing some cash flow relief.