Hi again everyone,
First off, thanks to all for the considered replies.
In answer to some of your responses, my post is semi-auto-biographical. Many years ago, I meditated in earnest for about six months, but without any knowledge of the stages of insight, or in fact any framework. In spite of that, I had many interesting experiences (recounted elsewhere on DHO), with one being truly profound, from my point of view at least. Not in an astounding, amazing, lightning-bolts-up-and-down-my-spine way (although I had these as a child), but in a calm, quiet, subtle, winking out of consciousness for a short time sort of way (also recounted elsewhere). Was it stream entry? Not sure. It changed me in subtle ways, in terms of understandings and perceptions. The following few days were wondrous. I was very aware that it was significant, but without a framework of understanding, I was not aware of its significANCE, if you get my meaning. At that point, it was just one more (remarkable) speed-bump along what I had assumed to be a fairly straight path ahead.
It would be nice to think that it was SE, but I am understandably wary of assuming too much. A few months afterward, I had what more typically equates with another A&P event, as described here and in MCTB. And shortly after that, meditation became difficult and frustrating (from what I can remember), and I simply stopped after a time (again, without knowing that this might have been expected).
In the time since then, there were very brief periods of practice, but more recently (for the last two+ years), I have been reading extensively, and practicing in earnest again (30 minutes, twice each day, more if possible). And I have spent some time trying to make sense of my past experiences. In my readings, I came across MCTB, and am very thankful for its contents, and the DHO.
My current situation is that progress has been very slow, relative to what I experienced way back when. I have no doubt about the value of my practice, but with whatever time I've got left, I would obviously like to optimize my chances of further progress, which is why I am wondering about mitigating the/any impact of so long a gap between efforts. How would that, could that, should that, affect progress? Again, my thanks for the feedback you have provided in this regard.
What next?
Everyone's experience is different...check.
Don't get obsessively caught up in the finer detail of the maps...check.
Just sit...check

Recently, having learned more about other meditative techniques, I've been doing more noting practice, both on the cushion and off (even on the subway), and have seen some progress. Not nearly as rapid-fire as my original practice, but territory that seems familiar in quality at least.
Cheers,
Patrick