Does Stellaris end at a certain time?
The game has no end based on time, this is why there actually are victory conditions (either control 40% of the colonizable planets or eliminate all other independent empires).
Triggering one of those conditions (either by you or another empire) will show an end of game screen with scores, but you are allowed to continue playing.
It makes sense for Stellaris to be this way, as it is unfettered by the historical constraints of other paradox games.