Although im not the most experienced, I have done slip casting for a few of my projects and may be able to help, bearing in mind my experience was in small quantities (30-40 pieces)
What are the duplicating molds made of? Plaster?
Definitely made of plaster, 2, 3 or how ever many part mould you want are easy to create by blocking in parts of your mould with moulding clay, pouring plaster, removing the clay and pouring the second half of the mould, ect. beware though, dont be shy on the mould release! or in my experience, vaseline. theres nothing worse than pouring the second half of the mould and not being able to separate them again!
How long will a duplicating mold last (molding cycles)?
As i mentioned, ive done 30-40 pieces of a small porcelain hip flask i did with absolutely no worries and no visible wear to the mould, people in the ceramics department i was in were doing upwards of 50 pieces and didn’t seem to have a problem either.
What is the cycle time usually? 6,8, 12, 24 hours? Can it be shortened by heating, etc.
Cycle times depend entirely on how quickly you can dry out the plaster between runs, although applying too much heat to evaporate the water will result in an exploded mould, but by placing my mould in the sun i could happily get through one every 12 hours or so. My advice would be to make a number of moulds, plaster is cheap and if you make one good master object, there no reason you cant cast 3 or 4 moulds from it and have them cycling through
Same restrictions as any "hard mold; draft, no back-drafts, multi-piece molds required if back-drafted, etc.?
Pretty much, i’d be generous with your draft angles, maybe 3/4 degrees, it depends on the part really and how much mould release you get in there. I have seen some pretty crazy moulds though, so it depends on how inventive you get with the moulding clay and plaster pouring, there are guys who can pull off 5 piece plaster moulds to make porcelain skulls, it can be really fun, but the best way is to just start getting your hands dirty and play around with it IMO!
Hope that was some sort of help!