We are at almost the same level (I just leveled up to 35) but for what it’s worth, I’m going much slower. I haven’t had a sub-two-week level since level 16, and I currently average around three weeks per level (or even longer if I miss a review day or two for whatever reason).
I find it horrifically demotivating if my success rate falls much below 85%. It must feel brutal to only get 50% to 75% correct!
Every now and then a bunch of old, poorly memorized items will fall into my daily review pile so my success rate drops considerably and it really feels like a grind. On days like that I put lessons on hold until reviews start feeling easy again.
As others have stated: just slow down and stop doing lessons for a while until the reviews start feeling easy again (with higher success rates). That will absolutely help with the number of apprentice/guru kanji.
The reviews will still suck for a while, but eventually you’ll start seeing some items so often that they’ll automagically move out of Apprentice — they’ll eventually become so familiar after seeing them so many times that you won’t even have to think.
What’s worked well for my blood pressure is daily reviews (just once a day), but try hard to get the number of reviews down to zero every single day. Only at the end of my daily session do I do lessons.
If I feel exhausted after reviews because I missed so many, I may not do any lessons. If I’m new on a level and still getting brand new kanji, I rarely do more than 5 lessons. If I’ve been on a level for a while and it’s mostly vocabulary to hammer home pronunciations, I might do fifteen or twenty if it feels easy.
My breakdown looks like this currently:
It honestly still feels pretty effortless. I get about an 85% to 92% success rate on most days. TOO high of a success rate means I’m not pushing myself enough and need to do more lessons. Too low becomes a grind so I don’t do any lessons.
Just let the SRS do its magic and don’t compound your problems by stuffing more and more into the Apprentice bucket.
15 days on a level is NOT slow! Keep doing reviews and the number of items in Apprentice will absolutely go down. Patience is a virtue.