I hate throwing anything away Mark. I have four Tamiya Willys MB Jeep kits, a Tamiya M4 Sherman - Early Production, a Tamiya M4A3 Sherman and two T23 resin M4 Sherman turret kits that I will probably never use or finish. I tell myself I am keeping them for parts, or just because they might come in handy someday.
When I started building models after 55 years, I did not have the skills or knowledge to even complete a simple project like the Willys MB Jeep. Plus, everything had changed since I was a teenager. New methods of painting and gluing had revolutionized the scale model industry. Model manufactures had advanced in tooling beyond anything I could have imagined when I was a kid.
So, I decided to stick with everything Tamiya: models, paint, glue, putty, and tools. However, in time I learned there are other great model manufactures out there in the market and other paint, tools, and supplies. Today I would say AFV Club kits and Asuka kits are my favorite, but there are many others. There is also nearly an endless list of aftermarket resin kits, tracks, metal barrels and photo-etched parts. The hobby has changed in an incredibly positive way.
To address the point of your thread, I give all my completed models away, to friends, veterans, veterans families and organizations. So, I have no shelf of completed projects in my studio (spare bedroom). I plan to eventually donate all my new and unfished kits to a local modelers club that has an active youth program. My joy comes from planning and building a model, not keeping it, sort of like 'catch-n-release'.
Harold