I know SE sites' community moderators are elected by the community. The last and only election on GameDev was in 2011.
Do these elections happen periodically or just that once?
From my understanding if there's pressure to add another moderator, or an existing moderator steps down, then they'll have an election.
I don't think existing moderators have to re-nominate themselves, it's purely an additive basis.
Do you feel we need another election?
I think they only happen when they need to happen, generally at most once per year; so far there's been no need for another one.