Once they have rooted properly in the pot, you basically can plant them out whenever you feel like.
However If you planted them densely in the pot, then I would wait until they go dormant and divide them then. Ideally you want to divide them before they start to grow a new root system. In your area it might take much longer for them to start doing this, but here the dormancy period can be very short. In fact they often start to grow new roots even before the old foliage have gone completely yellow. We have much colder and wetter summers here which would trigger growth sooner, so I assume you would have a much longer window of opportunity, but still it can be good to be aware of this.