Device with valid IP missing from device list

I've given the Nest issue more thought.  Can't "prove anything" because my Orbi no longer logs things (NTP, DHCP assignments, etc.), but that's a different thread.

I know that my Nest connects to the Nest Cloud when it boots up because the Nest is controlled by a smart phone or tablet app that connects through the cloud.  Until a person opens the app, why would the Nest send any packets at all?  I don't see any reason for it to.  What that means (to me) is that the Orbi might see a DHCP request from the Nest, respond and put it into the "attached devices" table.  As time go by without hearing from the Nest, eventually the Orbi says, "guess that device isn't active anymore" and drops it out of the table.

As a test, I opened the Orbi attached devices page and, sure enough, no Nest.  Then, I opened the Nest app on my phone.  It's 72 degrees in my house.  Boom.. Nest pops up on my attached devices page almost instantly.  Just for fun, I left the Nest app open on my phone and watched the Orbi.  In less than 2 minutes, the Nest disappeared.  Do something on the app, and it appears.  Wait two minutes, and it disappears.  Don't even have to close the app.

When I've done Wireshark captures of my home network, I've always been surprised at how "chatty" most devices are.  They are sending packets all the time.  Looks like the Nest only talks when it has to.

Someone at Netgear probably knows exactly how long Orbi waits before forgetting a device, but they  also probably don't look at community forums and would be prohibited from telling users anything.