Recurring assignments can be extended in bulk from the Extend recurring assignments tool.
Steps in this task
Click on Extend recurring assignments on the User tools panel. Note only assignments applicable to where you open the tool (globally or that specific project) will be visible here.
Add any filters for jobs and/or locations.
Choose the range of existing assignment dates - only those recurring assignments whose end period is within this range will be used.
Add any Groups or People types filters.
Click on Find assignments.
Select which of the displayed assignments should be extended, and the new end date.
Click on Extend selected assignments. This will take the chosen recurring assignments and move their end dates to the given date.
Selecting a new extension date that's before the date a recurring assignment is already extended through will not change the end date on that recurring assignment. For example in the screen above, choosing a date of 1/15/2013 would not change any recurring assignments already extended through 2/1/2013.
After using this tool, run the Index update tool - it will help connect newly-extended job slots to existing job assignments.