Ev training help

[pokemongarnet]

When EV training a pokemon do you need to battle a pokemon that gives you EV's from fighting them every single time, or just before you level up?

 

[NiKaNoRoU]

Fighting only one EV battle gives the same result, be it right before the level-up or way before it. Because you get the same points.
The thing is, the farther you are from levelling-up, the more battles you can pile up to your EV training.