I stopped using most of them around level 30 or so, not because I wanted to (the mnemonics are incredibly helpful), but rather because the radical system doesn’t accurately reflect how I think of kanji anymore. For instance, I just did the lesson for 剰. Wanikani lists the radicals as pine, mouth, and ribs. However, when I look at it I see the kanji for ride 乗 plus the right-hand side radical variant of sword 刀. So the mnemonic about ribs, pines, and mouths doesn’t really help me and I have to come up with my own about riding and swords. I also noticed that both 剰 and 乗 have the onyomi じょう which means 乗 is probably acting as a phonetic component, so I can use that to remember the reading rather than a mnemonic.
I wish Wanikani didn’t slavishly adhere to the radical system because it would be much simpler if they also allowed kanji to act as radicals. They often add kanji back in as radicals which helps, but you still end up with some unwieldy mash-ups like 惨 which is listed as being fish stick, hair, big, and pile, but it’s much easier for me to remember it as just being left-side heart + participate 参 and I just build a mnemomic around that.
I recommend doing the mnemonics as much as possible for as long as possible though, because they really are helpful when they work as intended.