I was talking with a friend the other day there about the topic of limiting the frames per second (FPS) in a video game when playing on your PC. The argument didn't end with a much clearer understanding than was originally the case and neither side won the argument.
Many people do not realise how important limiting the FPS in a video game can be for performance. Think about it this way, every piece of information a computer's graphics card needs to produce is more work for the computer.
If a computer monitor refreshes at 60Hz (around about 60 frames per second) then running 120 frames means that 60 of those frames are wasted. This is, technically, how V-sync works as well. Limiting the FPS allows the GPU to work on the next few frames without filling the GPU doing overtime.
What this means is that your computer, which could be doing other things like calculating positions of units in a game or something, cannot be done until those frames have rendered. This is wasted CPU and GPU resources.
So go on, try limiting your frames per second.