I'm a very sporadic user of it. I'll use it for a month or two and then go months without using it again. I like going back to it when I'm trying to focus on something specific or actually work through a book rather than just a lesson here or there. At the moment, I think the last time I used it was back during the summer, but I decided over the weekend that I need to enter some lessons in it and use it again for a while.
The big reason I use it is for the timer. I know I could set a timer on my phone (or steal the one off the refrigerator for a few minutes), but there's something about using the lesson timer in the practice tool that tells my brain that it's time to focus and work on something specific. When I do use it, I usually setup a practice schedule to do 15 minutes of warmup from either PSTM or BBSB then 30 minutes of lesson.
Thinking about it, kind of like you, I guess I pull it out and use it when I feel like I need a little structure in my practice.