3 month long levels, any suggestions?

You can get from 3 months per level to 2-3 weeks per level pretty easily, without doing anything too crazy. It really depends on how many lessons you do per day and how you do the lessons (plain WaniKani versus a script to optimize the lesson order), plus of course how you do your reviews.

So first things first. You said you do your reviews once per day, sometimes twice. To keep up a decent pace, it’s really important to do your reviews at least twice per day. This is because the first review after a lesson is after 4 hours, then 8 hours. To optimize, you should do reviews around 4 hours and 12 hours after the initial lessons. For this I usually recommend either doing lessons first thing in the morning, a review around lunch, and a review at night. Or, do lessons around 4 hours before bed, followed by a review right before bed, and a review first thing in the morning. To level up faster, keeping those timings (for the most part) is important, as is doing reviews 2-3 times per day instead of 1-2 times per day.

For lessons, do you do them every day or sporadically? If you tell me a target for how many lessons (items) you want to do per day, I can give you a specific suggestion on how to use [Userscript] WaniKani Lesson Filter to optimize your lessons.