I used to keep libraries of things that would be pre-setup, but each scene is so different and I would modify it so much each time that I stopped doing it. But yes, it is a good idea to have blend files with materials set up as libraries and to manage assets from. The Cubicity course is all about those things:
https://cgcookie.com/courses/cubicity-creating-and-utilizing-asset-libraries-with-blender
