For the first few turns I can imagine that everybody does it much quicker. The timer for the turn stops once the last human has taken their turn, then the new timer begins for the next round (which is why it is typically set to 24 hours, since you don't know when each turn will end precisely).
But yes, people do a single turn when they log in, and the game itself spans 1-3 months. It is for more relaxed play style, and typically they are more democratic games (negotiation of treaties/exchanges frequently done via email).
Unfortunately, none of them work in FfH since you need all players to log in from the lobby at the same time or you get an instant OOS (normal MP faces this issue as well, not entirely certain what causes it TBH, it is just not an issue in MP since everyone is right there and able to log in at the same time).