A nice side benefit of the new Ice Array upgrade for Ice Mine is that it extends the area that Ice Armor is active. With sufficient cooldown reduction, you can spam Ice Array and basically give yourself a near constant 50% damage reduction buff!
These screenshots show how far away you can get from the Ice Mines and still have the Ice Armor active. Not that it matters that much, since you can just recast it.
Active anywhere within the mine circles
Limit of distance in front of the mines (next two screenshots)
Limit of distance behind the mines