The Mass Haul Analysis should be refreshed any time that you make a change that could affect the results of the analysis. That means whenever you add or remove Haul Roads, Earthworks Sites (Waste, Borrow, processing), or whenever you change a cost of something (a material, a haul road, a collection or distribution cost), or whenever you change the material quantities - either on site through a corridor model change, or through availability of materials through a quantity or process change at an earthworks site etc. You should also refresh whenever you add or remove or Activate or inactivate Barriers on site.
Once you have a Mass Haul Analysis that you are happy with, and you move onto Balancing the Mass Haul and applying haul ranges, you really don’t want to be refreshing the mass haul analysis again, because that will clear the balancing that you have completed at that point and you will need to redo it.