Two weeks at present, although I'm hoping to get it down to one soon. For a one-off prop I can usually get it done in a couple of days. My work schedule being what it is, tho, I spread those weeks of work over a period of up to two years -- and have to add another two weeks "interest" as it takes that much extra time to figure out what I was doing last January and get back to it. Roughly working it out, about 1/6 of the time is modeling. UVmapping and rigging are the biggest chunks of time. When making distribution-ready stuff (not just stuff for my own renders) about a third of the time is thumbnails, promos, file organizing, and endless testing.