Controlling the FormsAuthentication createPersistentCookie expiration

In an ASP.NET MVC2 app, we have the standard login action...

if (ValidateUser(model.Email, model.Password)
{
  FormsAuthentication.SetAuthCookie(model.Email, model.RememberMe);
  ...

where the second parameter to SetAuthCookie is createPersistentCookie with the following documentation:

createPersistentCookie
  Type: System.Boolean
    true to create a persistent cookie
    (one that is saved across browser sessions); otherwise, false.

We would like to have the persistent cookie expire after 2 weeks (i.e., a user could return to the site within 2 weeks and not be required to re-authenticate. After that time they would be asked to login again).

How do we set the expiration for the persistent cookie?