Thanks so much for posting your question. The tricky part about these types of decisions is that we are normally in a good financial position when we have to make them. You really have to take consideration into what could happen in the future.
Before making the decision, read this article "10 Great Reasons to Carry a Big, Long Mortgage":
I agree being debt free is the goal, but I also think it's extremely important to stay liquid. It doesn't matter how much you owe on your home if you can't make your next payment. That's the reason I feel it's best to save up the money until you have enough to pay the mortgage off entirely, then pay it off.
It's also worth mentioning that you can probably out-earn your 4.5% mortgage (which is effectively 3.?% after tax....) in investments over time.
I hope that helps! If you'd like more specific advice for your situation (because I know so little about it at this point), I'd be happy to talk with you over phone or email. Feel free to contact me at the places listed below.
Thanks so much!
Branch Manager l Certified Mortgage Planner
The Tyler Osby Team l Fairway Independent Mortgage
Phone l 515.257.OSBY (6729)
Twitter l @tylerosby
Have you checked out our extremely educational blog? http://www.wealthwithmortgage.com