I was in for 27 years, and received a total of 5 shepherding visits. 3 of those 5 visits were in the last year I was a JW, and were not to really "encourage" me, but to determine my status as a potential apostate.
While I was an Elder in the 1980s, I went on many shedherding visits. What we did was looked at the congregation in three groups, 1.) Excellent Examples, doing very well, 2.) Average, doing okay, 3.) Weak, needing assistance.
We scheduled our shedherding calls on the "weak" as we were trying to keep within Jesus words of leaving the 99 to find the one sheep who strayed. So, if you were an average to strong JW, this is likely why you received fewer or no visits. Once in a great while we would get the notion that the strong need encouragement too, so we would schedule them in as well.
We had a body of Elders of 7 or 8. We often had 5 or 6 Elders show up for shedherding, and we took along 2 to 4 Ministerial Servants for training. So, we might have 5 pairs, and meet with two families per week each, for a total of ten families. Over a month that was forty families, or just about the entire congregation. That was the ideal schedule. It never worked that way for all kinds of reasons. I would say that at our best we covered the entire congregation once a year.
Jim Whitney