JSF ViewScoped is used for ajax calls. Bean object will remain in scope as long as ajax call will be made within the context of a single page.
You can use any one of the following 2 approaches as per your requirement:
1) Use ajax call to update your page.
2) Use Conversation Scope. (In case of Conversation Scope, bean object will remain in scope as long as conversation is active.You can begin and end the conversation as per your need.)