Final closure on this - The problem with sys_seo_links is closed. Root cause: Mail notifications were going out to the mail server, which was "slow" due to DNS issues. That caused the script to run for 20-30+ minutes when there were many mail messages queued. Perhaps - in the context of mail outbound, it might make sense to have a "max lifetime" for cron jobs for mail sending - so that the job will stop sending mail if its more than x time, so that other non mail related jobs can finish without issues. Just a thought