That's a tough question. My fastest PBEM game took about 3 hours. Me and a friend (he lives in Japan and I lived in California) set up a power session one day. We started a new game, everything random, but we ended up on the same tiny island. I had iron, he didn't, I did a swordsman rush and killed him. However, this was very unusual in my experiences. It's really difficult to say how long a PBEM games takes. If you have 2 people, it will most likely go faster than if you have more people. If you have 8 people, you can usually only do 1 turn a day, or 1 turn every other day. Since there are 540 turns in a game, one game can take well over a year. If you want to start playing PBEM games, my recommendation to you is start will a small game, say one or two other people. That way you probably won't lose interest if you are not a dedicated civ3'er.