How many devices or rather Zigbee traffic is too much for a rule? I notice a few of my rules almost always leave out a device or 2. Mostly my sleep rule which turns everything off, times opening it
or closing all my shades, or just rules with lots of devices in general.
Short answer: it depends! On the strength of your mesh, on your routing table, on your devices and how chatty they are, on the phase of the moon, and on the LIBOR. (OK, maybe the last two were an exaggeration.)
My mesh is generally pretty strong. I use a 100ms metering delay on scenes and that seems to work 100% of the time. My Ikea shades for some reason are particularly problematic so I use a 1 second delay with those. If I close all of them (there are 8) in a rule I use additional logic to retry if they aren't all closed.