Probably the biggest difference between private, weekly students, and distance (online) students is this exact issue - how long to practice one thing.
One week is almost never long enough to really get a concept down, so with a private student, I usually do thing "A" one week, then the next week we go over it and look for issues, but add a little bit of thing "B" to go along with it. That helps stave off burnout, of course, but also works to keep the brain more engaged.
The next week, we'll look at both "A" and "B" and usually "A" is at a point where it can simmer on low heat for a while. So we kick more into thing "B" and add a little of thing "C."
Over the next few weeks, we'll come back around to "A", "B", "C", and probably have added a little of "D" and maybe even an "E", depending on available practice time.
When you get to a point of diminishing returns on a lesson, it's time to put it on simmer and move on. Maybe make a sticky note that you're going to re-visit it in a week, but for now move on to something else.
In a week, revisit the old lesson and, with a little refresher, it'll likely be better than it was when you left it before. At that point you know you can put it down for good and continue to move forward. If it's still not happening, make a note and wait another week, but continue to practice other things.
I usually have 4-6 of these types of things going on at any given moment. New licks, new scales, new chord voicings, songs, you-name-it. The available things to practice on never goes away
