If your mortgage's interest rate is 4.5%, because it's tax-deductible, your
effective cost is only ~3%.
Do NOT prepay your mortgage!
Instead, invest your little extra money every month in index funds (pick
funds with no trading commission cost, super low expense, super efficient -
low turnover), don't overlook such little money each month, because after 10
-20 years, you will have sizable amount of investment, and over the long
term, market return should better double of 3%, if not more!