I don't think it matters when you plant Crocosmia. I wouldn't even worry about them not getting a lot of water for a couple months.
But, if you break apart the 'stacks' of bulbs, it will take them a year or two to bloom. Any corm with an 'eye' will grow a plant. The stacks provide storage space for the growing corms. If you divide them up, most will grow but not bloom until they start growing new stacks.
