It is recomended to change CVT Oil at 40-60k kms.
Since all of it doesnt comes out and new is mixed with old ones, It is better to change it at 40,000 kms interval.
i myself got it changed at 63,000 and my car has done 112,000kms, Sent my car to Toyota Western motors and they told me its good for another 10-12k kms.
Before changing you should check the condition of the oil.