The title is probably gets you most of the way there...
Say you have a Zigbee plug that you don't need all the time, like for holiday lighting. For the purposes of this conversation, it no longer has any rules or apps associated with it. (No 'in use by.') Do you simply unplug it and throw it in the box with it's associated lights, leaving it paired with HE for next season, or do you remove/unpair it, too? You definitely plan on using it again, but not for another 8, 9, 10 months.
For Zigbee, as long as I have a good mesh full of other routers ("repeaters"), I wouldn't worry about it too much. Zigbee devices are always re-routing, so as long as there is some way to the hub, one router shouldn't matter too much -- unless you have any picky devices on your network, like Xiaomi/Aqara ones.
That being said, if there are no apps using the device, it's also safe and easy to just remove it. As a workaround to make this kind of thing easy for myself, I sometimes create a group and use the group device (you could do this with Room Lighting too nowadays, even if it's overkill...) in all automations, then you don't have to worry about those, either -- just add and remove the device from the group as you add/remove it from your hub. And the next year, it doesn't even need to be the same device you add back. 
I have a Zigbee plug I use to control some Christmas lighting. I just leave it plugged in year-round as it does not use a lot of power and it serves as a Zigbee repeater. I have a lot of similar plugs, so my Zigbee mesh is strong. If I were to unplug the plug used for Christmas lights, it would not hurt anything. The problem with unplugging it is that I might not remember where I stored it. Leaving it plugged in solves that issue.
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