"We noticed that you haven’t used your Google Voice number in a while. Because phone numbers are a limited resource, it is our policy to reclaim unused numbers so they can be made available to new users."
Strong request to the google voice team that they do something so that numbers that are being actively used to receive 2FA tokens don't expire!
It sounds like if you receive messages only, but don't send any messages or make calls, the number will expire.
Posting this as a hopefully helpful warning to anyone with a GV number that uses it to receive important messages but not to send/call out.
