I'm thinking that throwing the Nest thermostat away and going with a
different brand or product that last longer then 2.5 years is the way to
go. It's very frustrating. They have a problem that needs to be
resolved.
My 3rd Gen Nest gave me only 2.5 years of battery life and now it is out
of warranty and they say I need to replace the whole thing. I think one
should expect to get more than 2.5 years out of a thermostat. What a
joke.