If rates jump 200 basis points in short order: Your payment doesn’t change, so there’s no immediate payment shock. Moreover, your extra payments reduce trigger-rate worries. After five years, you’d still owe about $10,300 less than the variable borrower making minimum payments. That borrower gets the worst of it: almost their entire $2,560 payment goes to interest at the new, higher rate, so their balance barely shrinks. (To simplify the illustration, this assumes the full rate change occurs immediately and remains in place for five years.)