Hi Monica,
I believe you can meet your expectations using the Recurring Flag when creating the SLA's in Service Entitlemens Workcenter > Service Levels View.
This is better described at the Help Document "Configuring Service Level Agreements" that can be found in the Help Center of your C4C.
"You can set the flag for Recurring for the Due Date for Response option. Each time a customer responds to a ticket, Due Date for Response will be recalculated according to the time you define for this milestone (in the Operating Hours tab under Time Ranges)."
Hope to have helped!
Felipe
