I don’t know how these were advertised when originally sold, but I think products like these ought to clearly display a minimum sever lifetime. Something like “Nest connected thermostat, with 10 years of guaranteed cloud connectivity” displayed relatively prominently on the packaging. Otherwise, if the vendor can arbitrarily remotely yank access to a key feature, then the consumer is being sold a false bill of goods.
Products are not services. If you buy a product that needs services to work, and at the time of purchase you are clearly informed that those services are subject to change at any time, you are sufficiently aware of the fact that product functionality may change at any time.
You’re still in the return window when you are presented with the service ToS.
Even if we're not going to require functionality last more than 0 years, the 0 year promise should have to be written on the box in medium or large text.