It depends on where you live, around here, you're lucky to get 20 people. There has been a gradual decline in tournament attendance, probably because of the internet. The same places that used to get 50 people are struggling to get 20. The largest tournaments get about 800-1000 and they can go on for a week. The World Open is 9 rounds, Chicago Open is 7, those are the biggest 2. Chicago is 4 days, World Open I believe has 1 round a day for 5 days, then 2 rounds on each of the last 2. Most of the one-day events are 4 rounds with about an hour per side. The big ones you have 2 hours for the first 40 minutes then 1 hour for the remainder of the game.
1. Nc3 e6
2. e4 c5
3. f4 Nc6
4. Nf3 a6
5. g3 Nge7
6. Bg2 d5
7. exd5