My whole party ate the giant mech's cleave in the garlean wave- full to dead. We were all laughing in chat. Every following fate had similar carnage, and one of our members got to be a moogle. Its really fun once you make it in.
As for the timer, for all we know it might be random and Aether was unlucky enough for him to not spawn for 10 hours.. but then that means there might be other 10 hour gaps or potentially worse gaps possible during the event. If a person has a busy schedule, they might be stuck camping on the weekends. I had just hopped on to send my retainers out before I started getting ready for work but was lucky enough to catch it shortly before the NPC poofed away *_*