Finished?? I don't anyone on this board is ever finish, because once you do assemble a complete Fett then you get in this vicious cycle of upgrades.
Seriously this is not a black or white type of question, how long it takes is a big variable, some folks have been working on their Fett for 2 years or more while others have jumped right on in and manage to piece one together in a few months. If you have a lot of money some where around $2500 you can buy everything ready made sometimes even completely painted. If your like me where money is a big issue (that being there isn't any) then that means constructing everything yourself, so then it is only a matter of how much time you can dedicate each day to the project.
Since we just adopted a 3 1/2 year old little boy, for me I don't have a a lot of time, maybe 45 minutes to an hour in the evening 3 or 4 days a week, if I'm lucky. So far most of my time has been devoted to doing a lot of research and designing templates and drawing blueprints. So to be honest while have collected probably 75% of the materials and parts need for a Fett I still have a lot of construction and finishing to do and I have been at it for nearly two years, though it certainly doesn't seem that long. Nearly all the templates and blueprints are nearly complete, still working on the gauntlets so I am expecting things to start coming together pretty quickly from this point on. My goal is to have it ready by April for Norwest Con here in Seattle.
Hopefully I haven't scared you off, all of the templates are posted here on the Dent and are available to everyone so that should save you a lot of time in building the pieces and there are some fantastic painting and finishing tutorials. The Search function is your friend, plus this is a great community of very helpful people so if you ever get stuck there is always someone here willing to answer any questions and help you get through the sticky bits.
Alan