Hard-wiring your LAN is the best way to achieve optimal throughput from any part of your network for the most devices.  But low quality cabling, switches, wireless hops, and interference can reduce the bandwidth available.

Just as the gateway eero does an every-other night speed test to the WAN/Internet, I would the ability to *either*:

1) Nightly or on-demand test bandwidth between individual eeros on LAN

-or-

2) Nightly or on-demand test of bandwidth from all individual eeros to the WAN

Either statistic will allow users to keep an eye on the state/health of the greater LAN... not just how fast the gateway eero can communicate with the internet.