statusreminder.rb

class StatusReminder
  class << self
    def send_reminders    
      offset = 0
      jump = 100
  
      while( users = User.eligible_for_status_reminder(offset, jump) && !users.empty? )

        users.each do |user|
          logger.info("StatusReminder: Reminding #{user}")      
          Mailer.deliver_status_reminder(user)      
          user.update_attribute(:last_status_reminder_sent_at, Time.now) 
        end

        offset += jump
        
      end
      
      logger.info("StatusReminder: No users to remind.") unless users

    end
  end
end

user.rb

named_scope :eligible_for_status_reminder, lambda { |offset, limit| 
{:conditions => ["
  status_reminder = ? AND 
  last_status_created_at <= ? AND 
    (last_status_reminder_sent_at <= ? OR last_status_reminder_sent_at IS NULL)", 
  true, 5.days.ago, 5.days.ago], 
 :offset => offset, 
 :limit => limit} 
}

def to_s
  username
end