My original set of BFG's were the Long Trail TA's. I didnt rotate them at all and ended up with them cupped real bad on the inside tread... all 4 of them.
My next set I rotated about every 7,500 miles and they wore much more evenly.
I cross rotated them like below...
I always heard it was not a good idea to cross rotate since it changes rotating direction. A Factory tech friend of mine said that you just dont want to do that on directional tread tires.