Your friends comment is probably the general point that if you pay off your mortage earlier, you may less interest, as you are borrowing the money for less time.
However, its not always a simple as that. you need to look at the reality of your current situation to decide what to do.
If you have €1000 to spare every month, the simplest and best thing to do with the money is save it. You might get a higher interest rate than the interest you would save off your mortgage and money will be available for you when you decide to downsize.
If you dont think that you will get another mortgage, are you hoping that the equity you release when you sell your home will be ebough for you to buy another smaller, cheaper home, If so, more savings will help this.
When do you intend to sell and how much equity do you think there is in your home ?