Almost a workaround. This was driving me nuts so I spent all morning investigating my LAN traffic to figure out what was going on.
TL;DR: workaround is to set your router to reserve an IP address for each LIFX Z’s MAC address. Each router will have a different way to do this. I have an AirPort Extreme Router. For this particular router you can configure this via Airport Utility by going to edit->advanced->DHCP and NAT->Reservations and create new ones.
This worked for several more hours than it had in the past. However, by 8 hours later, one of the lights had disconnected again. And another one soon after. So the below information might help - but there is still something that makes the LIFX Zs disconnect after a while. AUUGGGGGGH.
You should be able to get the MAC address by looking at the list of wireless clients while the light is correctly connected. Or you can use a LAN sniffer (I used LanScan).
I don’t know if the bug is in the LIFX firmware or other devices, but in my case two of the LIFX lights and my ecobee thermostats were getting the same IP addresses at different times. If the LIFX had an IP, for example, of 10.0.1.25, my ecobee thermostat would later get that same IP address. Most WiFi devices are resilient to this will renegotiate a new IP address when this happens. The LIFX Z seemed to just disappear if there was any conflict and never ask for another one until rebooted.
That’s what I surmised from my investigation - it’s likely an oversimplification of what’s going on. But it led me to try reserving IP addresses for 5 of my strips, and they have been consistently accessible the rest of the day (of course this might all change, but so far so good).
My router is configured to DHCP and give out dynamic addresses from 10.0.1.2 to 10.0.1.200. I picked addresses outside of this range for the reservations (10.0.1.230-234).
Screenshot of one of the reservations attached.