Can extra yearly mortgage payment cut loan term in half?

Scenario analyzed on 30-year product

DEAR BOB: I was told a long time ago if you make one extra home mortgage payment each year on a 30-year fixed-interest-rate loan, it will be paid off in 15 years. If that is not true, how many years will it take off the mortgage by making one extra payment every year? --Geri F. DEAR GERI: Your information is incorrect. However, depending on the interest rate on your mortgage, making an extra mortgage payment each year (13 payments in a 12-month period) will usually cut the term of your 30-year mortgage down to about 22 years. Purchase Bob Bruss reports online. Of course, if you don't plan to stay in your home that long, then there is little sense in making extra mortgage payments. This is the same principle behind the biweekly mortgage payments (which I do not recommend). Biweekly mortgages paid every two weeks are the equivalent of making 13 monthly mortgage payments each year. An easy way to make 13 mortgage payments every year is to divide your monthly principal and interest ...