The boss did not remain perfectly fit. Boss changed into 20 different forms. It wasn't impossible to kill. Failing Yahoo is failing.
Originally Posted by From Megagames
We've all encountered lengthy RPG boss fights that lasted for more than an hour or two, but an 18 hours long MMORPG boss fight might be a little too much.
The fight took place in Final Fantasy XI, where "Beyond The Limitation" guild fought a new boss, Pandemonium Warden, who changed into 20 different forms through 18 fighting hours before the band finally gave up.
"People were passing out and getting physically ill. We decided to end it before we risked turning into a horrible new story about how videogames ruin people's lives", said one of the guild members called Sylphet. "None of us doubt that Pandemonium Warden can be killed. We just call into question exactly what the development team thinks is reasonable from human beings."
Keep in mind that those 18 hours weren't enough to finish the fight. Beyond The Limitation guild members believe that at least another 3 to 5 hours are needed to kill Pandemonium Warden.
But yeah, ridiculously long fight is ridiculous.