Mortgage terms, 10, 15, 20 or 30 years and why?

[Carolyn Morales]

For Mortgages, including Primary Residence and Rentals, Do you choose 10, 15, 20, or 30 year terms and why? We tend to go fewer years, with the mind to pay down principal faster and so far all are buy and hold, with a couple paid off. What is the benefit of going 30 year terms? I have heard some say to never pay off mortgage, to leverage refinance for more properties to save on taxes, but the cost to refi is not free either.