timer in asp.net

Question

my timer is stops after 28 mins and i dont want stop it anyone know how could it is possible. timer code is:

 void Application_Start(object sender, EventArgs e)

    {

        

        General.conn_string = ConfigurationManager.ConnectionStrings["Calling_care"].ConnectionString;

        // Code that runs on application startup

        System.Timers.Timer myTimer = new System.Timers.Timer();

        // Set the Interval to 1 minute (5 sec = 5000 milliseconds).

        myTimer.Interval = 60000;

        myTimer.AutoReset = true;

        myTimer.Elapsed += new ElapsedEventHandler(myTimer_Elapsed);

        myTimer.Enabled = true;

        //general.insert_value_for_string("insert into tbl_test(appstart)values(getutcdate())");

        

        

    }