Paying more than the minimum on your mortgage from the first year saves interest for the life of the loan - much like nstarting a regular saving or investing program.
Scott Francis in his latest Eureka Report article - Advancing your home loan - takes you through 3 key benefits to be gained from paying more down on your home loan
You reduce the amount of your loan by the extra repayment.
Every future repayment becomes more effective.
You reduce the overall riskiness of your financial position by being ahead in your loan repayments.
Take a look at Scott's article for more details. Well worth a read.