Interesting to see this post so I’ll share my experience though I doubt it adds anything to the discussion. For about 2 years I ran my Pi 3B+ in the attic. Periodically it would stop feeding and be inaccessible on the network. It could take months for this to recur or it might happen twice in a week. In theory (i.e. as measured by my iPhone) the WiFi signal in the attic was strong.
The drops weren’t regular but often enough to be annoying. I ended up putting a WeMo switch on the A/C plug so I can reboot it remotely. Then I added a script to my NAS to check periodically if it could fetch data from the Pi and text me if it couldn’t.
Then I moved the Pi into the house, just below where it had been in the attic. This was the result of moving the antenna. I ran it this way for several months and never had a single network drop. About a month ago I moved the antenna again and put the Pi back in the attic. In that time it has gone offline twice. Nothing about the wireless network has changed, all cables and power brick the same and so on. I’ve never really gotten confident with that’s going on that causes this behavior.
However I have a number of IoT devices that use various WiFi chips and some of them have the same behavior of randomly losing network connectivity for no known reason and failing to connect. One of them, using the WINC chip, won’t even reconnect on a watchdog reboot - it has to be power cycled.
This thread suggests using the watchdog feature of the Pi instead. Does anyone have long term experience with how well this work out?