Mortgage rates haven't been this attractive in more than a year, good news for homeowners eager to refinance. Many homeowners have already jumped at the opportunity to lower their monthly payment, spurring a surge in mortgage refinancing applications. The rush to refinance makes sense, as even a slight drop in mortgage rates can translate into significant savings over the long run. Still, there are more variables to consider than the mortgage rate, including the costs to refinance, the time it will take to break even and whether to hold out for lower rates. Here are some key factors to consider.