This power bank supposedly is always on:
I use that one for my Hubitat UPS - it works great for seamless cutover.
Thought I'd come back with an update about these devices and my setup. I still have zigbee reboots but they're very sporadic with none of these devices in place. I had a plug go bad and decided to pair one of these up as it's the area I had purchased them for originally. I had a radio reboot about 5.5 hours after adding it. I didn't do anything and just let the system soak. It's been almost 4 days and no reboots or issues. It's not chatty at all. The only number that stands out is the Hub Actions. It's at the top of the list with 130, Zigbee Map Helper at 114 and then a Sonoff button at 8. I'm going to put 2 more in place when I get the chance.
For the craft enthusiasts, painting these (black, in my case) does not hinder their performance.
Just another data point with recently purchased Sonoff USB switches: I added 2 of them to a C-8 with 105 Zigbee devices already in place and they have been great. Each one was repeating for 6 other devices last I checked and signal strength was excellent with turbo mode enabled. I know you said they aren’t chatty, but did you look at the Zigbee logs or just device logs? The previous firmware version was extremely chatty from what @kkossev said. The ones I bought from Amazon have the newer firmware and the Zigbee logs are pretty quiet with respect to these devices. I plan to add a couple more since they seem to be excellent repeaters.
I’ll check the Hub actions for mine when I get home and report back.
EDIT: It turns out that I have several Homeseer z-wave temp sensors with ~1800 hub actions each after 28 hours uptime, and 32 each for the Zigbee usb switches, which are way way way down the page.
Both. And yes, the latest firmware addressed the chattiness and is available via OTA. Although no issues I'm still surprised at the hub actions. More so because I simply don't understand it.
I think it’s just from the driver doing health checks on the device. Someone will correct me if I’m wrong
I have health check disabled for that device. I have health checks on other devices enabled and I'm not seeing those numbers. I have previously read up on hub actions just for learning purposes. But, obviously, I didn't learn anything. 
I can definitely relate to that 
This is the other way around: the Sonoff device is periodically sending 'keep-alive' messages that require a response from the hub. That's why you see an unusual number of 'Hub Actions' on the device stats page. You can leave the healthStatus configuration as it is by default; it is passive and does not affect the Hub Actions count.
This is the way some of the Sonoff Zigbee mains-powered devices operate, and actively repsponding is the way that Sonoff, HomeAssistant (Z2M), and other Zigbee hubs are handling these requests. So does the Tuya Zigbee Switch driver that I recommend to use with the ZBMicro USB switch,
Make sure your Sonoff ZBMicro has a 'Software Build' version 1.0.5, the previous versions are way too chatty.
Read through this a couple times -- did these finally become stable?
Really appreciate any update!
I have 2 and they work great. Also good repeaters.
I have 4 of them and they have been working beautifully. Excellent repeaters after turning on “turbo” mode.
Are you both on C-8's? I haven't tried them on my C-7 recently, but they were unusable when I last attempted. Have been keeping them on my Smartthings mesh instead.
There was a firmware update for the plugs that generally seemed to help:
I think they were very chatty on the older firmware iirc
C8Pro
I have 4 of them on my C-5 and they work great
appeciate it – will have to give it another shot after an firmware upgrade