I just started using SolidWorks again after a year or so hiatus.  I remember finding an answer for this but it was also debated.  Fully defining a cylindrical part.  Some people say not to, the less mates the better.  Some say to fully define, less for solidworks to solve.

Which is the answer?

Examples:  Nut that is welding on a hole.  Shafts where you dont need motion in your assembly.  Etc.