I have played this game for over a decade since Dota 1. It just doesn't get boring. There is always something new that you can discover in terms of the mechanics of the game and play styles of each unique hero. You can't just master all the 100+ unique heroes in this game at the same time. I think my own curiosity is the key that has enhanced my dota experience this far. Dota is evolving and that is what makes the game entertaining.