If you have everything printed and all the supplies on hand, screw sizes, wiring and everything you need and more or less know what you are doing. Only a few days if you were not going for cosmetic jobs and know exactly what you are doing.
In most cases people are building the robot for the first time and don't know exactly what they are doing so it takes time to get into the groove and fill those knowledge gaps. Calibrating servos, calibrating for potentiometer placement, potentiometer extraction, finger tension, etc etc
Of course printing taking the most time. Nextly learning how to use it with myrobotlab will take a little time to get things worked out as well.
So the answer is......it can be done fairly quickly......depending on your print and material situation and knowledge of the general how to process.
Will take some people a year, take some people a month, all depends on your setup. I'm fairly sure I could put one together in about 3-4 days with all the parts preprinted and materials on hand at this point. Wouldn't be a fun few days but doable. :9