@Azeez K. A few questions popped up from your post:
1. If the 6.45% 15yr loan worked in the investment plan for the property when it was acquired, what has changed that makes the plan worth changing?
2. Only by running the numbers completely will the cost/benefits of refinancing vs. staying with the current financing over the next five years become clear. That includes the differences in amortization as well.
3. One other thing to include in the analysis is that you may end up paying for three or more sets of loan fees and costs by going to the shorter term, good for the bank but make sure to include those in the calculation.
4. The last one is where will the property be in the market cycle in five years? How likely is it to be a period where refinancing is expensive or non-existent? Given that if financing were hard to get, selling at a decent price might also be hard to do, what would your strategy be?
Good hunting-