Six-months seems be the entire: start>finish process, as many have mentioned. The team is not locked in a room and then 6 months later emerge; "we have done it! we have created a new set!" I'm sure more than one set is in the works at any given time, and a lot of time is spent going through channels and getting feedback and approval :yada yada speculation:

The gear also seems to be designed around form fitting with any other piece of equipment. I have no idea how they pulled that off but I am sure it is not easy! And the complexity of the skeletons and weight painting has got to be a total nightmare in order to properly incorporate the motion-capture they use. I'm sure one month alone is spent tweaking the shoulders so when you lift your arm you do not look like a coach in a football game

If your curious though you should check out the equip files in the XIV directory. This isn't the days of XI anymore! equips aren't just a 3-D model with an image mapped onto them, it is some pretty large and sophisticated series of folders and files to create one working in game model. I think it is client>chara>pc>(race folders)>equ

If a company ever makes better looking models, and claims to do it faster, I would be very interested in their methods