Create one common Mock or one per Unit Test

I am currently expanding my Unit Testing using Mock objects (nSubsitute in this particular case). However, I wonder what the current wisdom is in creating Mock objects. For example, I work with an object that contains various procedures for capturing and processing data - there is no biggie here, but it will be used in a large number of tests.

Should I create a generic function that returns a Mock Object with all the appropriate methods and behaviors that mock a large part of the Testing project and call this object in my unit tests? Or I will cheat on an object in each Unit Test, only making fun of the behavior I need for this test (although there will be times when I will mock the same behavior more than once).

Thoughts or advice gratefully received ...