I don't pin for the small units, but as soon as I'm matching more than three seams I pin liberally. It's about knowing the goals of the project, and my own Return on Investment in the ratio between preparation and rework.
The QuiltCon 2018 catalog is out, and I'll be teaching! Check out my class and all the awesome classes, lectures and panels at the #quiltcon website. Looking forward to seeing you in Pasadena next February!