At max speed, it’ll take about a year. It gets really overwhelming at the end though at this speed, so I don’t think rushing is the answer.
For reference, here’s my timeline for completing WaniKani:
I initially came in with a mindset like you, aiming to get finish WaniKani as quickly as possible, and so I did everything as it came to me. Over the last few months though, even though the final levels only need half the time of most of the previous levels, I still took roughly the same amount of time for them as I felt overwhelmed because of the number of lessons I was doing, despite doing a few hours a day.
I’m not saying you shouldn’t rush it - I did it and I’m still fine - but if you do, I’d make one recommendation: don’t do all of your new lessons for every new level you reach in one sitting. For the first 30 or so levels, I did this, and as a result I would get huge batches of reviews almost every day in the later levels. Take your time, and only do a portion of them each day. I’d recommend doing 15-20 every days, and getting the reorder script to sort your lessons by newest level’s kanji and radicals first.
TL;DR: It’s fine to go fast, but don’t overwork yourself either. Just remember this graph from here (a great post that you should read btw) that even if you get 100% accuracy, the work will pile on if you don’t moderate yourself. Burnout is a very real thing.

(As a side note, I’d recommend using KameSame to accompany WaniKani for studying vocab. I’ve learnt a few thousand words with it over the past year and a half, and I’d recommend it if you want to learn vocab with a SRS system similar to WaniKani.)