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.
"Subway Surfers" is an endless runner mobile game developed by Kiloo and Sybo Games. The game does not have a specific end or conclusion, as it is designed to be an endless runner that continues indefinitely.