In simple terms all custom surfboard (not necessarily wake surfboards) manufacturers strive for a 2 week completion time (then add about a week for packing and shipping, if all goes well). Special orders can even be turned around in less than a week, and technically any competent shaper/manufacture can complete a board start to finish in 1 day (if all the materials are right there). However, the board will be weak having not had all the cure/post cure time necessary, whether epoxy or polyester/vinylester resins are used. 'Modern' epoxy/polystyrene boards require more time, both shaping and laminating. There are simply more steps involved and longer cure times and considerable temperature sensitivities for the epoxy resin. Add in complicated spray (paint) or print graphic art, or technical fabrics (carbon, kevlar, etc.,),or veneer laminates, special traction or fins, and the completion time will go up.
All and all, a custom board shouldn't take longer than 1 month once you and a manufacture have agreed on a price. However, delays can occur due to many factors. Everyone is relying on someone else (and some people do go on vacations), be it a foam manufacture, fin manufacture, graphic artist or print house, etc. Your average board has 5-6 primary components, none of which come from a single manufacture.