Relatively new postal laws prohibit mail services from using "suite" or "apt" or any other description implying a physical address. Reportedly this is because too many scam artists were operating from such addresses and then couldn't be tracked down (a case of legitimate box holders suffering the consequences of criminal deeds by others...). The box number now has to be in the format "Private Mail Box" or "PMB". Some of the old form addresses still exist where the local USPS Postmaster hasn't refused to deliver mail so addressed.
Postal laws require the mail service to obtain a physical address, but that might just be something like a campground. Problem with a temporary address is that the state driver's
license laws usually require notification of address change within 10-30 days or something like that. Interestingly, an actual Post Office box cannot be obtained without a "verifiable local address".
"Now if you earn money in another state, you may loose your Texas residency and be required to establish a new Domicile in the state you earned the money. This happens when people work as camp hosts in Oregon, and other states."
The above is not entirely correct -- If you earn money in a state, you must pay taxes in that state, and if you meet a 'physical presence' test, the state can consider you a resident for tax purposes on ALL your income (I know Calif and Utah have these provisions), but a person is never forced to domicile in another state. It seems that there is a basic right for each of us to declare a domicile, but it is possible to mess that up by seeming to claim domicile in more than one state.
The word residency has different meanings even in the same state and is used in context, like Fishing, Education, taxes, etc.
It can be a real mess in the US if one is a FullTimer or a traveling worker (software contractor, welder, etc.).