In reply to TobyA:
I wear them all the time (climbing, running, gardening, sleeping (sometimes)) I'm wearing one now, I like having different colours. 2 of my griffons are threadbare and my wife says I don't need two red midlayers, so will be offloading that one.
I don't need more, but I would like to diversify the colours and brands of an item of clothing I get a lot of use out of.
I say "fetish" as a humourous way of describing my enjoyment/attaction to an item of clothing. I could've just asked people to "list lightweight midlayer waffle fleeces", but I like to jazz things up.
To address your point on not consuming more - I get that. I could not buy more, and if I was just hording for no reason other than for dust gathering I'd agree. However, I do use them, each of them and often. I could buy one at a time and wear until destruction, or I could have a few and rotate it all works out the same in the end.