It’s still better to set some timeframes, otherwise interest in the tournament will be lost, as happened with the "Third World War," which still hasn't ended. And there was so much hype at the beginning.
There was a war like that back in 2006, a major event in the world of Heroes, with online and offline players participating, playing Heroes II, III, and IV. There was a huge clan war, and it ended completely; everyone finished playing.
By the way, there's a tournament on HP right now where you can win $100 by completing an offline map. It would be interesting to know if there are any who can even just complete it.