When to press the macro

Hey guys, so I was playing and testing out some macros (new to WoW and Macroing) and I was wondering, does it matter if I am pressing the key as fast as I can? Or should I be pressing it waiting for the cast to 100% complete and then hit it again? Does it matter? I was wondering if I am missing abilities when I spam it as fast as I can.

Thank You!

I keybinded 1 & 2 from the keyboard not numpad to the scroll up (2) and scroll down (1) 1 being your main ability and 2 being your aoe. If you macro in say your cd’s you can put this on key 3 and only press that key when you need them. But to answer your question spells only go so fast so you can pound your keyboard to a pulp if you’d like. But the cast time of that spell won’t change if you beat that crap out of your keyboard. There is latency timing you can change. I just scroll at a fair steady pace the next cast may be an instant one??