Well, the answer is seems isn’t that easy to define.
ProSound web recently compiled a range of answers from their forum and put them up as a blog. Interesting reading, for sure.
Personally I can have a mix together in around 30 minutes. [Post-edits, track arrangement and bussing.] Getting the final result is often down to collaboration between myself and the band, so that can take anywhere from 20 minutes to 5 days with multiple final revisions.
Article can be found here!