What are the benefits of making an extra mortgage payment at the end of the year?

I am tring to sell my house. If I make an extra house payment on 12/31/08, will that benefit me?What are the benefits of making an extra mortgage payment at the end of the year?
If not selling your house, the benefit is years of saved interest expense.





If selling, don't do it. Keep your free cash in case things don't go exactly as planned - if the money is left over, put it down on the new house.What are the benefits of making an extra mortgage payment at the end of the year?
In addition to saving interest expense, you can write off more of the interest in your 2008 taxes when you file taxes in 2009.