Thread stops after it has been in a loop for a few hours. (while loop)

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C#

multi-threading

I am unsure why this code stops after running fine for hours. I have a hunch that it has to do with threads being aborted automatically, garbage collection? The project is a winforms project.
Any help would be greatly appreciated!

And here is the code:

public void InstantiateListenerAndResponder()
       {

           try
           {
               var t = new Thread(Listen) { Priority = ThreadPriority.Lowest, IsBackground = true};
               var t2 = new Thread(StartResponder) { Priority = ThreadPriority.Lowest, IsBackground = true};
               ThreadManager.AddThread(this);
               ThreadRunning = true;

               t.Start();
               t2.Start();
           }
           catch (Exception ex)
           {
                var se = new SystemEmailer();
               se.SendMessage("ERROR CODE 104 - \n" + ex.Message);

           }
       }


       private void Listen()
       {

           try
           {
               while (ThreadRunning)
               {
                   try
                   {
                       GetMail(ReceiverEntity.UserName, ReceiverEntity.Password, ReceiverEntity.IncomingUrl, ReceiverEntity.IncomingPort, ReceiverEntity.SecurityType == "SSL", ReceiverEntity.ReceiverId);
                       var se = new SystemEmailer();
                       se.SendMessage("ASR CHECKED EMAIL AT: " + DateTime.Now.ToString());
                       Thread.Sleep(30000);
                   }
                   catch
                   {
                       var se = new SystemEmailer();
                       se.SendMessage("Error checking email. Will try again." + DateTime.Now.ToString());
                   }

               }
           }
           catch (Exception ex)
           {

              var se = new SystemEmailer();
               se.SendMessage("ERROR CODE 103 - \n" + ex.Message);
           }
       }

       private void StartResponder()
       {
           try
           {
               while (ThreadRunning)
               {
                   ExecuteResponder();
                   Thread.Sleep(ReceiverEntity.ResponseInterval * 1000);
               }
           }
           catch (Exception ex)
           {
               var se = new SystemEmailer();
               se.SendMessage("ERROR CODE 102 - \n" + ex.Message);

           }

       }