In general, most tournaments will fill up and close within 72 hours of the first participant who completes their game entry.
How quickly your tournaments will fill up and close will depend on a variety of factors - the most critical factor being how many players are playing a specific tournament type that are of similar skill level to you as determined by the WorldWinner matching system.
The less players who are of a similar skill-level to you that are playing, the longer the tournament may remain open.
If you find yourself having to wait longer for your tournament(s) to fill up and close, It is recommended to try out the different tournament types or try a different game title on WorldWinner to see if other tournaments/games are filling up quicker.