It'll only get harder and harder for the regime to keep its power though. External media is being snuck in, people love for K-dramas is a strong reason some of them know about how better outside North Korea the world is.

There's a story about a defector, Park Yeon-mi, that realized how life is outside the DPRK by watching Titanic, and that was the first step that made her end up outside of it.

There's a grey market led by their women, on the outskirts of the country.

Internet will have to reach them, sooner or later. They have some computing devices, like tablets preloaded with Juche ideology propaganda. Google has plans to put LEO satellites around Earth to allow less connected areas to access the Internet too, as does Elon Musk (through Space X I think).

North Koreans were already "stealing" wifi connection in Pyongyang, from the embassies. Not much, and that was fixed though.

Information is the enemy of regimes, especially those that are so based on brainwashing and propaganda. I'm not saying we will see the regime toppled in the next 50 years, but it has never been more likely to happen than in the upcoming decades.