Hi Jessica, thanks for the time to let us know of your experience with your Nest Learning Thermostat. We’re sorry to learn that you had to deal with the connectivity issue twice, and about the warranty replacement process.

The Wi-Fi disconnection issues may be related to a power issue. Your Nest Learning Thermostat is designed to get power from your heating and cooling system wires. If the system wires can't deliver enough power, the thermostat battery will start draining, and this results in your thermostat limiting its features such as Wi-Fi connection to preserve battery. The resolution may be to install a common (C) wire in your system to deliver constant power to the thermostat. The power resolution will also help fix the connectivity issue. We recommend contacting a Nest Pro technician to check your system first and install a common (C) wire if needed.

Also, with Advanced Exchange, we’ll provide you with a link to order your replacement device and it will be shipped to you before you need to send your defective device back. This way, you’re not without a device. Please note, this option will require an authorization hold on a credit or debit card for the full cost of the device. But once your defective device is returned, the authorization hold will be removed from your card. To be clear, this hold is not a collected payment so the amount will not be deducted from your account.

We'd love to answer any of your queries, you're more than welcome to visit us anytime here: https://support.google.com/googlenest/gethelp