We have been in our home for 10 years. Our principal has really not gone down very much each year until now. Last year (April 07-April 08) we reduced our principal by 12K. If we follow along using our debt reduction snowball, we will reduce our principal by 14K next year and an additional 16K the following year.
Each year the amount of the principal reduction will be more because our interest owed will not be as high.