Back in Gen 5, EV training was still very similar to the current way it is, but with a few main nuances related to numbers.
- They actually let you max all the way to 255 back in these days, but because this number is not divisible by 4 and 4 are required to move the stat by one in most cases, this was pointless and it was always more useful to pray that those extra 4 EVs saved you in something. This was changed in Gen 6.
- Without having prior knowledge of this, you may have made the mistake of maxing them all the way to 255. Not the biggest deal in the whole world, but not the absolute best.
A side note, my goodness, God bless you for having used those wings to train a Pokemon all the way to 252 EVs.