I think above 60fps there is no visible difference in video. The main reason wanting this as high as possible is so that when there are a lot of enemies, etc on screen, the fps does not drop enough that video becomes slow or jerky. In other words, you want the average fps to be good enough that the low end is still acceptable. In twitch games (shooters, etc) a high fps helps with targeting, etc.
As long as the demo/game does not slow down significantly, whatever value you get for the fps is good enough.
