I did it in 43 hours, about a month from start to finish - flying a couple sessions a day when weather & availability permitted. I think that definitely helped speed things up...this was in the R22.
Long gaps between lessons adds to the total time, you forget stuff. Trying to cram in too much at once also is counterproductive.
In my case I also had about 800 hours of military crewmember time - that helped at least from the standpoint of not being freaked out from being in a helicopter in the first place, I also knew how to read a map & communicate.