Tyre rotation for 4X4s

It's fine to do either a 4 or 5 tyre rotation. Just DO rotate the tyres around once every 10,000km.

I do a 4-tyre rotation so the spare always has as much tread as possible - that way if I come to use it then it's got the least chance of a puncture.  However, that leaves you with 4 worn tyres and one good one, which in theory could carry over to the next set, but tyres do age and eventually become useless over time even without having rolled a single metre.  This is a particular problem with caravans which do low mileage. 

Once th four are worn out you have a few options - by another four of the same tyre and use the old spare on the rolling wheels and one of the new ones as the spare, or use the old spare as an emergency sixth-spare, or sell it.

The most cost-effective way is a 5-tyre rotation, the risk-averse way is 4 tyres.

One other note - the tyres need not always rotate the same way.

While on the subject of tyres the manufacturer's recommended pressures are likely to be a bit low.  The stronger, tougher all-terrain and mud-terrain patterns don't dissapiate heat as well as passenger tyres, especially in light-truck construction.  They therefore need a couple of extra PSI, and also consider if your car is anything like the normal offroad tourer it probably has anywhere between 50 and 300kg of kit of it beyond the standard tare weight.