The box says the game length is 10-30 minutes. This is a simplification and part of the issue is how many players there are, and if everyone needs to read all the cards. Once people are familiar with all the card abilities, they tend to play a lot faster.
My current general estimation is the following:
- 2 players: 5-10 minutes.
- 3 players: 10-20 minutes.
- 4 players: 15-30 minutes.
- 5 players: 20-40 minutes.
- 6 players: 30-60 minutes.
- 7 players: 40-100 minutes.
- 8 players: 50-120 minutes.
One deck is only made for two to four players, and two decks can be shuffled together for up to eight players. These estimates are mostly based on new players of the game, who will want to read all the cards.
My recommendation is for 6 and 8 player games to use teams — two players per team can each take their turns at the same time and still act as separate individuals. If a player wins or loses, the whole team wins or loses. Use minimal communication with team members. Some is okay, but don’t spend two minutes or more planning everything together. Teams can speed things up a bit when done properly.
I mostly recommend to play 2-6 player games, especially for new players. If you can find eight people who are all very familiar with the game, then that might be worth playing. However, the game often feels too long once you get 7 or 8 players.
Some people have said they can play one game for hours, even with experienced players and only four people playing. If that happens, I recommend taking one or two cards out that cause a player to draw cards. There is no reason the game should go so long unless players forget that the Eights are wild cards or something happens when players repeatedly keep causing others to draw cards.
Do my estimates seem accurate based on your experience? You can let me know in the comments.