Assume you have a 500k fixed rate mortgage until 2025, then variable. You want to hedge the interest rate risk, how would you do that? You could buy puts on GBL (10 year Bund) but you would need to roll them annually and they seem very expensive: 1yr ATM costs roughly 5k for 150k notional. So for 500k you would buy ~3 contracts every year. Are there better (more liquid) products?