I'm not sure on the exact timeframe, I guess it depends which position you are in the que. SUPPOSEDLY they review the auctions before posting. It takes a lot longer than it should though. IMO they should credit you that extra time on your auction.
My "blah" items show up instantly. For example, I posted a pair of no-name brand shoes for $0.99 and they were immediately searchable.
All of my brand name stuff (especially the really high end stuff) takes at minimum of 12-18hrs (I've timed it) to become keyword searchable (comes up under ID#). I got a vague response from ebay that this had to do with selling restrictions placed on my account because I hadn't amassed enough feedback. I've also *heard* that during this "mystery" time, they're authenticating and checking for legal stuff. Who knows :-\
I will say this, I posted a Cole Haan bag the other day in addition to the "blah" shoes. Posted within minutes of each other... shoes immediately searchable... Cole Haan bag is not. Doesn't show up for about 16 hours. I'm annoyed but then I noticed - ebay credited a full DAY to the auction!! So the "blah" shoes are ending when they "should" be ending... whereas the Cole Haan bag is ended a day later than expected! Soooooo strange but I'm not complaining