The most significant advantage to learning the timing is that you can focus more on delaying jC properly in case you are too high for the 5c 3c to land upon an immediate jC.
Well, BB runs at 60 frames a second so each frame is 0.016666~7 seconds in theory, but you have to take into consideration frame skipping and your display's refresh rate.
There are other variables to consider, but they're mostly minor.