I have 8 retainers and as a crafter with all crafts 50 or above all my retainers are nearly full with mats, melds, glamour, weapons and gear. Not only do you need space as a crafter for normal mats each one has a HQ alternate also. To say you need a hell of a lot of storage in this game to enable you to be a high level gatherer and crafter across all disciplines would be an understatement..