All the time
I swear I made this thread the other day, but I must have pressed cancel instead of post. Anyway, I honestly forgot I had them most of the time. Hopefully I'll remember in the full game, especially bottleneck battles.
I had yet to fully get in the habit of using them. And I don't think I used the Black Wax Idols even once, since I only managed to find one or two of them. I usually tend to hoard most of my cash and items in RPGs until I have a decent amount.