Do you really want to spend time debugging home automation that didn't function because the Ecobee or other remote servers are down again? I'm tired of wasting minutes of my life on that, and that's why I bought a HE.
The only reasons to connect an Ecobee to the web at all are:
- remote access from a phone (when their servers are up),
- collection of data for the pretty graphs (only works some months),
- integration with other home automation gadgets (sometimes works),
- software updates every few years.
If you don't need those things often, just disconnect it from the net and keep it offline entirely, and it functions just fine as a thermostat. Same reason as buying a Hubitat - things work much more reliably that way. Simplify, people - don't make things unnecessarily complicated, unless you actually like fixing broken stuff - don't use a computer when a simple switch will do the job.