Interesting question.
I experienced a sweet taste and a corresponding sensation of bliss many times with the nectar technique (AKA 'khecari mudra'), mostly while sitting in meditation. Getting the tongue way back up there is really not necessary whatsoever.
The attendant bliss would not wear off right away, and occasionally lasted hours.
Once in a blue moon, I will still experience it while sitting (but without the technique).
Having said that, I have no idea how the hell it happens, biologically or otherwise, but it did happen (as sure as is typing these keys at present).
I highly doubt these flash experiences are sustainable, and do much more than to let us know that just MAYBE there are things that we cannot always explain away (as 'snot' for example) and that there are enjoyable experiences available in the 'inner realm'. On the other hand, I think chasing these experiences can do more harm than good, and create more angst than pleasure actually.
And of course, are not singular to GMJ, Knowledge or any other tradition.
M
