Actually I've only invested in one new camera and a new used lens. I still have my old camera but think about to sell it. But I would never sell my old lenses because I select new lenses not bases on the age of my equipment but on what I need.
That's why I decided to buy a used Sigma 70-200 f/2,8 lens instead of the Canon EF 100mm f/2,8 macro lens or the Laowa 25mm 1:2,5-5 lens. I needed the Sigma lens more than a new macro lens and so I keep my equipment as long as needed but sell it afterwards.