Quote:
Not only will Patch 2.4 implement the addition of the new Rogue class and the new Ninja job, but also a large increase to the number of plots of housing land. Accordingly, data-handling capacity will need to be increased, and for this reason, we will be conducting database optimization with this maintenance in order to aid in load reduction and increase data processing speed.
Database optimization will require time. In addition, because these are vital servers that house our players’ precious data, extra care and precaution must be taken. As a result, this will be a prolonged maintenance lasting 24 hours.
It's outside the realm of a normal patch, because of all the server side work required. They detail it pretty well with the lodestone announcement.