I have multi-page form where I pass an object between pages as follows:

On each page:

// What page to go to next
private void btnContinue_Click(object sender, System.EventArgs e)
{
  if (Page.IsValid)
  {
       MyXferObj obj = new MyXferObj();
       obj.dataitemX = somevalue;
       obj.dataitemY = somevalue;

      Session["MYXFEROBJECT"] = obj;
      Server.Transfer("nextwebpage.aspx");
  }
}

// Re-populate the page controls, handles "back" button and postbacks
private void Page_Load(object sender, System.EventArgs e)
{
  if (!Page.IsPostBack)
  {
     if (Session["MYXFEROBJECT"]  != null)
        RehydrateObj();
  }
}

// Re-constitute the "pass-along" object and use the data fields required
for this page
private void RehydrateObj()
{
  // cast the stored obj to MyXferObj type
   MyXferObj obj = Session["MYXFEROBJECT"] ;

  ... Repopulate the page controls with the values from "obj"
}

My questions are:
1)  I'm concerned about memory leaks - do I need to "release", set to null
the MyXferObj somewhere?
    At each page, my Session["MYXFEROBJECT"] would be set to the "latest"
incarnation of a new MyXferObj - do I
    need to free the "old" one somehow (if so, how?) ?

2) Is there a more preferred way to pass information between pages?  I
prefer to have a single "data-struct" object passed if
   possible, rather then creating an entry in the Session object for each
data item.