Some of us make rich scenery with a lot of figures and props which need a particular style. So I never uninstall things because I might need it later. I occasionally use stuff that is 7 or 8 years old.

How you organize it, is a matter of taste and workflow. I use a 3rd party database (PzDB) which finds things within seconds and I can select the ones I want. I have set up my runtime with subfolders and break them up into more logical structures when they get too large. With the new library and the scrollwheel it is extremely easy to navigate through the tree.