With the tools the shop has the size of the blade makes little difference in how long it takes to finish. With that said, I watched a fellow get a knife hammered out of a railroad spike, shaped, and quenched in one 6 hour session. It was his first time working at the forge. All he had left to do was temper it a few hours in his oven, and do the final clean up sanding.

I would say 3 to 5 days working time would suffice unless you've got little to no experience shaping materials or never have a large chunk of time that can be devoted to it. A day or 2 to shape the knife and get it quenched, a day to anneal it, and however long it takes you to clean off the remaining scale, polish it suitably, and put an edge on it.