It depends on what the events are doing.
If you are checking collisions on hundreds of objects then that particular event will slow down the system, especially if it's doing it every tick.
If all its doing is setting an objects opacity to the same value, then no it won't adversely degrade fps, .....unless you have hundreds if not thousands of instances doing that.
Adding extra events to stop it setting the opacity don't add any overhead either.
Unless you have hundreds if not thousands of instances doing that every tick.
So basically, adding extra events to stop unnecessary repetition are the way to go.