The most common cause of M3U streams stopping after 30 minutes is a timeout mismatch between the player and the server. Xtream UI may not be handling idle connections efficiently, or your CDN is cutting off inactive sessions. To fix this, ensure your playlist uses a keep-alive header and check your server's nginx.conf for send_timeout and keepalive_timeout. On the player side, using an app like IPTV Smarters with “auto reconnect” can help.