i haven't done the ND, so probably should comment, or at least be first to comment, but as this is now on Page 3 of recent posts, at least I'll bump it to the top again.
I guess the when to start and stop thing is quite personal, depending on the individual's personal goal for the ND. If it is to lose x amount of weight, or to achieve a fasting score of y, that's obviously quite easy. If it's something far more amorphous (without medical intervention), like defatting your organs, I'm sure it's much trickier, given Professor Taylor's documented personal thresholds comments.
I note you are now in the healthy BMI range, which is marvellous, and an achievement in its own right, so very well done fo that. That may be enough to achieve deatting of your organs, and certainly your consistent blood scores evidence that, to an extent.
On the cautionary side though, I would encourage you to look at your calendar and perhaps plan the next couple of months, from a health management standpoint? By that I mean, have a serious review of what you have achieved, with a short period of normalisation?
I can't recall if you have had abdominal scans prior to beginning the diet. If you have, I'd be inclined to get another scheduled in, now. If you haven't, you're probably going to have to use a bit of guess work. Have you noticed any trimmings in your middle are when on the diet?
For some people, the ND way of eating could become addictive. For some, the feelings of shrinking (and to an extent, hunger), will feel like markers of success, due to the consequential results of trimming and weight loss. If you are one of those people, don't stay on it too long; it could be difficult to stop if you do; by virtue of losing sight of "normality" and satiety.
You are about to go away for a week, where I am guessing your usual routines and eating patterns are likely to be disrupted, so that may not be a very helpful marker for you. But, it is a good opportunity to try to revert to what you want to be something like your everyday eating routines/diet?
After a total of eight weeks, you are likely to have achieved much. So, why not, on the back of your enforced break, try a few weeks of eating the way you want to, post-diet. I'm not suggesting that should necessarily be a carb-tastic lay rice, chips and bread fuelled feasting, but a migration to how you want to live your life. Don't forget Professor Taylor talks a little about modest weight gain, post-diet, and that you may have some enzyme lag, as your body readjusts itself to digesting more food, and more varied meals. After, say, a month, you might have a more personally valid view on your need, or otherwise, for another stint. If, at that point, you want to trim up further, you could probably still achieve that by a carb reduced diet, but more balanced, and at a gentler pace? After, again, say a month, you will be beginning to see blood data to influence your then next steps.
Apologies this is such a long post, but it sort of grew as I typed. For me, again reiterating I didn't do the ND, I found the latter phase of my reduction and transition to a more usual way of eating far, far harder than the trimming of body and bloods. I have had to constantly monitor my weight, by with a view to maintaining its floor; not guarding against gain, so that is something to consider - especially as getting that balance has involved increasing the fat element of our diet, which we all know is a battle with our own counterintuity, usually.
Good luck wit it all.