I used to do legs 2-3 times a week, but it seemed to make things worse for me (knee injuries/groin) had to stop training legs for 1 month or more, since changing to once a week i am able to push much harder and noticeable size increase in legs.
Keep in mind i had previous knee troubles. Although i do miss that pain you get after the legs a still a little sore and you start hitting them again 2 times a week.
If you can, do the legs as often as you feel.
Most of the boys where i go don't do legs, i think they will regret that choice later down the track.