I used to hoard stuff, but no longer.

Especially if you are an omni-crafter you should be able to keep only a limited stock of items.
I suggest keeping only HQ/hard to obtain/very expensive items on your retainers, and simply buy (and/or caft) the rest when needed. And when your stats are high enough you might not even need HQ mats anyway. I myself have cleared out most of he random mats I had lying about. I always told myself I might need them one day, but after my retainer had them for months it was pretty obvious that was not the case.

TL;DR: you don't need such a huge stockpile, get rid of it.