We split this question off into it's own thread since it's a bit different that the original.
Take a look at the Resolving Multiple Prompts for Credentials Knowledgebase Article. Multiple Login Prompts often occur when the Tableau Server is not part of the browser's Trusted Sites list.
If the steps in this Knowledgebase article do not correct the issue then I'd suggest submitting a Support Request so that we may investigate further.
If your users are authenticated they will not asked to provide their credentials again (except timeout stuff, what you can simply increase to a reasonable one). Could you specify your requirement more precisely, just to make sure that I am understand you