title: NTLM Security - how long before it times-out and is not valid
body: <p>A user on a mobile device navigates to a web site/page protected by windows ntlm security.  The user provides their credentials and uses the site.  They walk away and return later and they are not required to re=enter their credentials..</p>
  
  <p>Question: What determines how long the authentication is valid? How best can we limit the time that it is valid before they have to re=enter their windows credentials?</p>
  
  <p>thx</p>