Extending Forms Authentication Timeout When Making AJAX Calls With jQuery

$.ajax('ajax.php',{timeout: 60000},function (data) {
alert(data);
}

<WebMethod(CacheDuration:=0, EnableSession:=True)> _
Public Function keepSessionAlive() As String
    If Session("UID") Is Nothing OrElse Session("UID") = 0 Then
        Throw New ApplicationException("Login")
    End If

    Session("lastKeepSessionAlive") = DateTime.Now

    If Not (Context.Request.Cookies(System.Web.Security.FormsAuthentication.FormsCookieName) Is Nothing) Then
        Dim ticket As System.Web.Security.FormsAuthenticationTicket
        Try
            ticket = System.Web.Security.FormsAuthentication.Decrypt(Context.Request.Cookies(System.Web.Security.FormsAuthentication.FormsCookieName).Value)
            If ticket.Name = Context.Session("UID") Then
                System.Web.Security.FormsAuthentication.SetAuthCookie(Context.Session("UID"), False)
                Debug.WriteLine("keepAlive:AuthenticationReset")
            End If
        Catch ex As Exception
            Debug.WriteLine("keepAlive:AuthenticationReset FAILED!!!")
            Throw New ApplicationException("Login")
        End Try
    Else
        Debug.WriteLine("keepAlive.Load: No Authentication Cookie. Error")
        Throw New ApplicationException("Login")
    End If

    Return Session.SessionID.ToString
End Function