This article discusses how often you need to authenticate when using IWSaaS.
You are required to perform authentication thirty (30) days after the last login.
This is based on your browser's cookies. If you deleted your browser's cookies, you are required to authenticate again. Closing the browser will not affect the authentication.
Authentication does not apply across all browsers. This means that if you use Internet Explorer, IWSaaS will require you to authenticate and then if you use Firefox you are required to authenticate again. Authentication per browser is stored within 30 days.