6 IEMs of various manufacture. No customs, as I don't listen to IEMs that much.
Yes, that's a BUNCH.
I tend to sample the offerings along a line from manufacturers whose sound sig I appreciate. And then, I suck at parting with them, once acquired. And I can be kind of selecting a specific set of cans for a specific music and amp pairing etc. etc. yadayadayada. To be fair, I only buy earphones from those brands that I like the sound sig. If I listen to something and don't like the ss, I absolutely never buy.
And many MANY of my acquisitions are used minty. Kind of a recycling, and I have less run-in time to manage. Oh yeah. CHEAPER, too.
Well, I tend to keep them in any hard cases or carry bags they come with on a set of shelves in my big room and above my computer/Woo-stack station. I don't hang them much because I think doing so puts stress on the structure of the headset.
Any that aren't in their specific case gets laid on the shelf, and, if gimbals permit, with the ear speaker flat on the shelf. If I am actively listening to a set of cans, they typically are set aside on a table suface adjacent the rig that is playing them.
IEMs stay in cases provided by the manufacturer.