The game was written to play at 30fps, so 30 to 40 is right there. A US TV show used to be broadcast and 29.97 fps, which of course was interlaced. You do not "see" any better differences with the higher frame rates in the game anyway, and might actually eventually mess with the game's "time" clocks. It is better to stay closer to 30 than 130... my opinion. The harbor traffic brings the game to life for me, seeing other boats and ships buzzing about, with the occassional airplane flying overhead. Not too many though, because they are resource stealers...
