Really depends on how artistic the bow is going to be. Ie... footed riser, horn or antler overlays, etc,ect....
for a plain Jane bow probably about 15-20 hrs. For a fancy bow probably 30-40 hours of actual hands on and that is spread out over several days or even weeks between curing times for each step of build and finishing.
Ps.. I can usually build about 3-4 bows in the time it takes to complete one by working on the others between curing times.