Dear Less Experienced Jax Users
When you activate your E, no top laner is going to sit there an AA you. You can press E again to use your stun way earlier, there is no reason for you not to. I won a lane against the last 3 Jax' I laned against because the let their E go the full duration. The stun time doesn't change so let it rip.
You'll never be able to stun a

etc if you let it go the full duration.
Against Fiora, it'll actually be the worst decision you ever made lol, you have to vary the timing against her.