title: Persistent cookie timeout with FormsAuthentication
body: <p>I am creating some "Remember Me" functionality as part of logging in.</p>
  
  <p>When I create a persistent cookie during the login process with the following:</p>
  
  <pre><code>FormsAuthentication.SetAuthCookie("someusername", true);
  </code></pre>
  
  <p>And my Web.Config looks as follows:</p>
  
  <pre><code>&lt;authentication mode="Forms"&gt;
    &lt;forms loginUrl="~/sign-in" timeout="2880" /&gt;
  &lt;/authentication&gt;
  </code></pre>
  
  <p>How long will the cookie be valid for before the user will be asked to provide their login details again?
  Also, Is there/What is the default length of time used when setting a persistent cookie?</p>