簡言之，重貸合算與否，要看 total interest over the life of the PROPERTY. 從此意義講，重貸劃算否，當然與貸款年限，還剩多少年有關。因此，如果你想付清房貸，do your math. you will save after refi if
- you keep paying what you paid before monthly, or
- you pay off your old loan balance in remaining years under new loan rate, in your example, 4% 20 yr fix.
事實是，許多地主並不想迅速付清貸款，或不打算長期持有，這種情況下，人們更在乎的是降低 monthly payment 以增加現金流. 低利率的重貸可以達到此目的。
