Merit gem cron job to check and remove temporary badges

I have a badge rule like this;

grant_on 'comments#create', badge: 'frequent-commenter', to: :user, temporary: true do |comment|
  comment.user.comments.where(:created_at.gte => (Date.today - 30)).count >= 20
end

User will lose the badge after sent a comment. But s/he will have the badge forever if s/he doesn't send a comment.

Is it possible to check temporary badges and remove the ones which are not valid anymore?

Can't run from the merit rules, as the comment local variable won't be there from a cron job. What I'd do is move the logic to the user model, and then call it both from the rule and from the cron job:

grant_on 'comments#create', badge: 'frequent-commenter', to: :user,
  temporary: true do |comment|

  comment.user.is_frequent_commenter?
end

class User
  def is_frequent_commenter?
    comments.where(:created_at.gte => (Date.today - 30)).count >= 20
  end
end

class RemoveInvalidBadgesJob
  def perform
    # Better done by direct database query?
    User.all.reject(&:is_frequent_commenter?).map do |user|
      user.rm_badge(1)
    end
  end
end