How slow do you want to go? I’ve been doing about two weeks a level for almost my entire WK career, which is a slow pace for some, and a fast pace for others (in total, it will have taken me about 2.3 years to reach level 60). According to the heatmap script, it has averaged out to about half an hour of work a day. That’s with doing WK every single day, though, without taking breaks.
I agree with everyone saying that it’s best to review every day no matter what. The way the SRS works, your study decisions will come back to haunt you hours, days, weeks, months later, so I personally recommend doing a consistent number of lessons each day that results in a manageable daily review load that you can plan for and clear every day without too much trouble regardless of what else you have going on in your life.
For me, that was 12 daily lessons for the majority of WK (I ended up reducing that number in the later levels because there were fewer items per level, and I have more leeches now that take up more time). I used the lesson filter script to mix the kanji and the vocab lessons for even more consistency (1 kanji for every 3 vocab is a good, stable ratio).
If you haven’t read it yet, I recommend taking a look at the ultimate guide to WK for tips on scheduling. Even if you aren’t trying to speedrun it, it’s helpful to know how the SRS works and how to fit WK around your life to achieve the pace that you want. It’s easy to adjust the number of daily lessons down and still make good, steady progress.
Definitely get your reviews down to zero again before taking more lessons, though. I recommend doing that gradually. Reorder your reviews (by SRS stage is probably best, which you can do with the reorder omega script) and choose a target number to do every day (like 100), and gradually chip away at the pile until you reach 0. That way, they won’t come back in huge clumps later down the line.
If the pile is too large, you could reset back a few levels to reduce it. Anything that was at guru stage or below is almost certainly gone from your memory and will need to be relearned anyway, and probably most master stage items and many enlightened stage items as well.
Good luck!