Is my performance affected by invisible items? I am making a video and I am planning to have a particle emitter to shoot lasers from my spaceship. My theory is to somehow keep it going endlessly, but control its invisibility somehow, perhaps with drivers.  

Would it still be running in the background while invisible, thereby affecting the performance?
Like is it still running in the background while invisible?
-> if an object is in the renderlayer, whatever the color (even invisibility) blender will still compute it ( so it will decrease performance).
If you don't need this object you can put in in another renderlayer that you don't use.

but control it's invisibility somehow
-> you can use a keyframe on the color of the material to make visible/invisble at the moment you want