Hi there Caryn, thanks for sharing your experience with us. We can only imagine how frustrating this may have been for you, and we apologize for the shortfall in providing you with your support needs.
All carbon monoxide (CO) alarms expire because their sensors have a limited lifespan. To comply with certification standards, 2nd gen Nest Protect has to be replaced after 10 years, while 1st gen Nest Protect has to be replaced after 7 years. Because CO sensors have a limited life expectancy, certification standards require Protect to chirp after its sensors have expired or have failed. To help you remember to replace your Protect before it expires, you’ll receive reminders long before your Protect’s expiration date. If you have any other questions, we'd be happy to answer them, if you can reach out to us once more using this link: https://support.google.com/googlenest/gethelp