I am NOT generally a collector of things, but when I take up any hobby, I will buy whatever supplies I need and/or want to pursue those interests. As it sits now, I have an 8 shaft weaving loom and a mountain of yarn for that all collecting dust, and more skeins of knitting yarn than I will ever use. I took up quilting a few years ago and have acquired a comfortable amount for me. From time to time I will start to feel that there is too much money sitting around in fabric, and I'll just stop buying until I've completed some projects. Knowing that I am a little fickle when it comes to hobbies, I have finally learned to keep my accumulating under control. What I always have to remind myself is that there will always be another sale, there will always be new fabrics out there that I will like just as much if not more than "the one that got away". I practice my self control on a regular basis, as I just spent about an hour looking through all the fabric on sale at Craftsy. Tempted by several things, but then I think about what I already have and just move on - at least for today.
I do not "kit" anything until I am ready to start working on that project - just prefer to always leave my options open and be able to see everything I have when creativity strikes.
As is evident by the responses, everyone has a different way of thinking (one might say rationalizing) about their "stuff", some being comfortable with abundance, others not so much. It would not dawn on me to compare the amount of stuff that I have to the amount of stuff my husband has (I win, by the way) but I've seen many comments in numerous threads related to that. Always an interesting topic!