Why do you think they will be EOLd? https://support.google.com/product-documentation/answer/1023...? Shows they are guaranteed to be updated for at least 5 years after release, so you have at least 2 more years, but hopefully longer. Only 1 nest product has stopped receiving updates so far and there are several that are 4 years past their guarantee date so precedent would indicate you still have a fairly long support window. This isn't the same as supporting a phone.