login control - keep me login until I logout

in the login control event loggedIn

protected void LoginControl_OnLoggedIn(object sender, EventArgs e)        {            CheckBox cb = LoginControl.FindControl("RememberMe") as CheckBox;            if (cb != null && cb.Checked)            {                string userData = "keep user login";                // true if a durable cookie (a cookie that is saved across browser sessions) was issued; otherwise, false.                bool isPersistent = false;                string username = LoginControl.UserName;                FormsAuthenticationTicket ticket = new FormsAuthenticationTicket(1,                  username,                  DateTime.Now,                  DateTime.Now.AddYears(1),                  isPersistent,                  userData,                  FormsAuthentication.FormsCookiePath);                // Encrypt the ticket.                string encTicket = FormsAuthentication.Encrypt(ticket);                // Create the cookie.                //Response.Cookies.Add(new HttpCookie(FormsAuthentication.FormsCookieName, encTicket));                 // Create the cookie.                HttpCookie cook = new HttpCookie(FormsAuthentication.FormsCookieName, encTicket);                cook.Expires = DateTime.Now.AddYears(1); // if not set the expire date, the cookie will removed after browser closed                Response.Cookies.Add(cook);            }        }

// get the how many minutes total and left to logout, form authentication

public class FormsAuthenticationHelper    {        public static double GetFormTimeout(Page page)        {            HttpCookie cookie = (HttpCookie)(page.Request.Cookies[FormsAuthentication.FormsCookieName]);            // if no user login, the cookie will be null            if (cookie != null)            {                FormsAuthenticationTicket ticket = FormsAuthentication.Decrypt(cookie.Value);                double timeoutInMinutes = (ticket.Expiration - ticket.IssueDate).TotalMinutes;                return timeoutInMinutes;            }            return -1;        }        public static double GetTotalLeftFormTimeout(Page page)        {            HttpCookie cookie = (HttpCookie)(page.Request.Cookies[FormsAuthentication.FormsCookieName]);            // if no user login, the cookie will be null            if (cookie != null)            {                FormsAuthenticationTicket ticket = FormsAuthentication.Decrypt(cookie.Value);                if (ticket.Expiration - DateTime.Now > 0)                {                    double timeoutMillisecond = (ticket.Expiration - DateTime.Now).TotalMilliseconds;                    return timeoutMillisecond;                }            }            return -1;        }    }

// how to use 

double currentTimeout = FormsAuthenticationHelper.GetFormTimeout(this.Page);                if (currentTimeout <= 60 * 24 * 30 && currentTimeout > -1)   // if the page has timeout in a month                    your function();