Workplan Resources, Update Periodic Amounts only shows next 12 months

Hello,

We have a project that is scheduled to finish Dec 31, 2017.  The user wants to change the workplan distribution of the labour hours for the resources.  When they go to the Update Periodic Amounts screen, it displays the next 12 months, and the remainder is grouped in a Succeeding Periods period.  She is certain that in the past she has been able to see the periods all the way to the end of a project.  Is there some setting that determines whether all periods are displayed versus only the next 12 months, or is she mistaken about being able