how to optimize 勧告 retention without burning out

I hit hour 912 of my Anki core deck and 勧告 (recommendation) is killing my retention rate. It dropped to 43.2%. To fix this, my Phase 1 sub-routine is to isolate 勧告 and drill it every 120 seconds over a 4-hour hyper-focus block while listening to its audio loop at 1.5x speed. Phase 2 is mapping it to related terms like 軍事 or 最上 to build a semantic spreadsheet grid. Anyone else doing high-frequency micro-drills?