Advanced Japanese Learner--how long would it take me to reach the last quarter of the course?

I have a suggestion for how you could use WaniKani (assuming you like it) to learn the kanji/vocab you want to without going through the whole year+ course.

Once you subscribe (even for only a month), you are able to view all the radicals, kanji and vocab on the site. You could then download the (free) userscript called “WaniKani Self Study Quiz Edition”. This allows you to test yourself at your own pace even on locked items (i.e. items that haven’t come up yet in your WaniKani lessons). And that way, you wouldn’t need to waste time on things you have already mastered.

Doing it that way, you wouldn’t be using the built-in SRS, but you could use the tool and your own self-discipline to really study the kanji/vocabulary you need to, using the nicely laid out WaniKani website. This might be a convenient option for someone with a lot of kanji knowledge already, and even better if like many people, you didn’t enjoy using Anki.