I have run into several customers having internally users loginning each time using the companies external crm address. This can cause a bit of anger with your CRM users.
Each ADFS system has an internal URL. This URL can be found by openning up the ADFS Management Console or Using the CRM deployment manager. Using the CRM deployment manager, right click on CRM and hit properties, and navigate to the web tab. This is the internal URL.
The internal URL will pass the domain credentials (Kerboros) and not force the user to login each time. The CRM users will love you!