What happens to the remaining amount (25 years of costs) that have not yet been deducted if I refinance again now?
Actually, it depends.
If you refinance with the same lender, the remaining fees on the original loan are added to the fees of the new loan, and the total is amortized (not capitalized) and deducted (not depreciated) over the life of the new loan.
If you refinance with a different lender, then the remaining amortized costs of the old loan are deducted in full immediately, and the fees on the new loan get amortized and deducted over the life of the new loan.
