8 tyres or 10 if you have a tandem axle van, regularly rotated will give you best value, life expectancy and less likelihood of a puncture.
Most tow vehicles tend to wear their tyres much quicker than a van or camper, which is more likely to crack rather than wear out. Most punctures tend to happen when the tread is in the latter stages of its life.
So rotatating tyres on vehicle, trailer and spares will not only prevent more punctures and give you better tyre life / value for money but you are also unlikely to suffer a blowout from a tyre with lots of tread, but that is perished and brittle from old age
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