Players who want to continue gaining full experience after the eight hour mark will be forced to change classes. Once another class is selected, players will have eight more hours to gain full experience. Afterwards, they will have to wait seven days in order to return to a job class and gain full experience again. While this may sound like a solution for more experienced MMORPG players, there are a finite amount of classes, meaning there are a finite number of hours players can play per week.
According to Final Fantasy XIV director Nobuaki Komoto, the purpose for Final Fantasy XIV is to allow players who have little time during the week to fully enjoy an MMORPG. Komoto describes the fatigue system as something similar to what happens when people get tired in the real world. While this may seem fair for gamers with responsibilities like school and work, it doesn't change the fact that gamers will still have to pay a monthly fee and not be able to play the game to its full potential.
[Source: FFXIVCore.com via Kotaku]