As already stated - depends on the hair and the honer.

My hair will rarely pass the HHT on a professionally honed blade - nor with that blade tree top my thin wispy arm hairs. I still find the HHT useful but I mostly use SWMBO's hair at the very end of honing and after stropping. Since I always use pretty much the same progression on the same hones (Shaptons) I know the final edge will be pretty much the same. I find the HHT more entertaining than anything - just knowing that I've succeeded in creating a very sharp edge is all that it tells me - I like to make the HHT as high a bar as possible - holding the root end of the hair and gently probing the edge from 2 inches out to see if it silently cuts. If it does, I giggle and shave with the razor knowing that it's sharp and if the shave doesn't go well, I know there is something else that I'm missing. As time goes on and you get better at honing the shaves get better and better and the HHT becomes less and less a test and more of a novelty.

-john