For a normal type black hole (which are still theoretical, although there's reasonably good evidence for them now, but whether they actually contain a singularity or not is not know) containing the mass of at least several of our suns, Hawking (as in Stephen Hawking, who postulated this type of radiation) would take an extremely long time, probably longer than our universe has existed so far. However, for a singularity with a mass of only a few gold nuclei, or part of one, it could conceivably occur very quickly. This is way out on the fringes of theoretical physics, though, and quite possibly there is a simpler explanation. Pretty crazy stuff if true, though.
Hawking finally had to admit there isn't any...