Car import timeline

Our family of 4 are looking to move to Ethiopia soon from South Africa.
We are thinking about driving to Ethiopia.
What is the longest we can stay with our vehicle in Ethiopia before having to "import" it?
Should we come in with a tourist visa for a few months, can we stay that year with our vehicle without importing it?
Also, if we have an off road trailer (not one where we can sleep in, but one with a camping kitchen, tent etc), does that have to be imported as well?
Thank you,

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