annual inspections & registration on extended trips

This isn't an RV only problem. Tens of thousands of US military personnel are stationed in states far from their home state where their vehicles are registered and licensed. The same policies normally apply to RVs in many states.

For Texas - if your vehicle is out of state, you get the registration renewed by mail with a statement the vehicle is out of state and unavailable for inspection.

Then when you return to Texas, get the vehicle inspected.