If you notice, when you play the game, the tracks of the Subway always lean towards the left and the direction of the tracks never changes. So, I believe the Subway Surfer will never stop running because he is running in circles so, the game will never reach an end.

The game's design is based on continuous running and avoiding obstacles, so there is no specific end point or final level. Players can continue to run and collect coins for as long as they like, striving to achieve high scores and complete various challenges.