Assembly: System.Web.Security.SingleSignOn (in system.web.security.singlesignon.dll)
As part of Federated Document Collaboration (FDC), SharePoint clients can share Office documents across a federation using SharePoint as the resource application. This type of scenario will use NT impersonation tokens for authentication.
If the WebSSO cookie expires and the client has a document open in an Office application for edit, then when the client attempts to save the file the operation will fail. The solution to this problem is to set the token lifetime directly on the application. The token lifetime is configurable for each trusting application through the TokenLifetimeInMinutes property. This lifetime applies to the SAML token issued by the resource federation server. Because the SAML token is also used as the Web server authorization cookie, the same lifetime applies to the cookie.