So I did my efficiency testing and it passed with flying colors. I put one PD stem's worth in the nipple stem. (It ended up being about half what I normally put in there. I think this stem can hold a total of three to four PD stems.) I got one big hit, a second wispy one and two more ghost hits. I normally get thicker hits from the PD on the last two hits, but the first one is so thick on the HI that there isn't any vapor left to be had. So I can cache a PD stem's worth on two hits instead of four...that's a good thing. The effect has been good...just a little lift, which is about what I expected since I have needed two to three times that amount to get there for a while now. Interestingly, I have been getting blasted by the HI off just one stem, which equates to two to three PD stems, and that's what dose I was at with the PD back in the day. After this I put a ridiculously small amount of herb in the stem...maybe a third of a PD bowl or less. I got a good hit off it and it was done. The hit was thick at first but died about halfway through. The fact that I could get milk at all with this miniscule amount really impresses me.
So, two conclusions:
1 -- this thing can quickly and efficiently vape as small amount an as you wish; and
2 -- I have no idea how lwien has been getting by off just one stem a night for so long!