[kube-system]

> So it's somewhat possible.

It's definitely not possible to have a mail forwarding box as your primary residence.

> But I'm curious what people do in more dynamic housing situations.

In situations where a primary address is ambiguous based on number of nights, many tax authorities will consider other aspects, such as the address you have listed on government documents, where your family lives, whether you use any of the properties for income or pleasure, where you work, etc.

Also, if you change primary residences, many tax authorities will simply pro-rate your taxes for the period of time that you lived there.