If I remember correctly FP didn't take that long to set up.
Personally, In the past I've spent a good 3/4 weeks preparing a forum and never actually opened it. Needless to say that wasn't such a great idea. Why? The longer you delay the opening the more time you have to change your mind and convince yourself it's a bad idea.
Lol, it's been months for mine that are still "pending" 😛
I haven't really ever kept track of time it takes to set stuff up, but I know my "free domain guide" site only took a few hours. Forums require more work though.
Probably about a week has been the quickest just online. I like to spend some time with preparing, making notes, working on little odds and ends before actually setting it up though so if you count that the quickest one would probably be about 4 months actively working on it.
It took me roughly two hours for me to set up RX Community. I carefully thought out of what the forum layout was to look like so that it is "unique" to other forum layouts.