I try to be consistent with my level times, and what I’m noticing is that the further I get, the harder it becomes. Before leveling up, I always try to make sure my lesson stack is 0, but the past few levels have been a real challenge and I got really backed up during the last level, getting up to 170 lessons. I was able to knock out about 30-60 per day for several days, and now it’s back down to 50.
A big obstacle of this speed is that it will be mid-December before I actually burn anything, and I started at the end of June. At my current pace, I’ll be around level 24 at that point, and until then every lesson that I learn from levels 1-23 will be in the review piles.
On the levels where I’m able to keep less than 3 kanji from resetting SRS stages, I level up in about 7.5 days. The days that are about 8.5, I got more than 3 wrong which reset their stages. The longest level up was level 4, and that’s because I took a few days off for a family vacation.
The reason I’m going at such a fast pace is that I want to move to Japan as quickly as possible. I figure being able to read will be pretty useful! I practice by reading all 3 context sentences for each vocab lesson, and looking up words I don’t know. It’s very time consuming to do it that way, but I’m able to because I prioritize WaniKani over everything else right now, except school and work.
All that being said, you should go at a pace that will push you just barely beyond what you think you can handle. The most important thing is to pace yourself and make sure you don’t lose determination. Stay diligent and do not what makes you comfortable necessarily, but what pushes you to be better! If going quickly makes you want to stop, then there’s absolutely nothing wrong with going slowly. Consistency is much more important than speed.
I presume you are a One Piece fan 
But if miraculously the annual offer happens this year, I’ll be much more patient with myself.