Legends are nominated whenever they come up. If someone catches the eye then someone may just put up a blurb about them out of nowhere. There's no timeline or quota or anything.
Once a few legends have been nominated and decided upon to be accepted the newest additions will generally be publicised in a group or a wave. Normally that accumulates every few months but it's slowed down now that most of the past legends are there. Now it's looking more and more to the current community and who is outstanding and a role-model now.