The wifi APs too. And not "will" stop working but "might, and if so I won't be around to reboot it." Also regularly tests that stuff will return to health after a real power outage, and that nothing is depending on ephemeral state like DHCP leases. Basically, I want to experience the same circumstances during the week I'm visiting that they're going to experience for months after.
Ubiquiti APs failed this test. The moment one started an OTA update, my mom temp unplugged it to make room for a blender. It soft-bricked itself. Parents couldn't figure out how to reconfigure it after a hard reset.
I usually SOIC clip/backup the firmware on Ubiquity and other devices we own, before doing anything like this (more recently). Its usually so much faster and reliable than an RMA in most cases for a simple firmware update fail, especially with the post pandemic supply chain the way its been.
Took awhile to get the approval but when you have a large pile of RMAs sitting for 6mo to a year due to a bad firmware update, for only a standard 1-2 year limited warranty, and they stop responding, and replacements were back-ordered for ages. Well, you do what you have to.
For wifi in the kitchen. The walls have wire mesh that happens to block RF really badly, so wifi will only work in the same room. If internet went down, house was also a cell dead zone so nobody could talk to me while looking at the router or something.
Usually the power brick is poorly isolated and/or you have dirty electricity, it results in errors on an ongoing basis that get logged to the small amount of onboard memory. (not usually a circular buffer.)
When the errors have sufficient volume the memory fills up, and it stops working at resource exhaustion.
In a real pinch, I've resolved this in some of the more milder cases by simply using one of those walmart plug timers that turns off for a few minutes in the morning when everyone is asleep.
Well, at least they were on UPS and got power conditioning that way. But there's also just crappy programming. It's not only ISP-provided stuff, it's cheap home routers in general. I don't trust them.