I feel like opinions about what ābigā and āsmallā are is going to differ. Maybe a poll with specific number intervals would show some interesting results.
I never do more than 150 reviews in a sitting, when I do have more than that I take a hour or so break inbetween. I think I prefer about 100 in a sitting. Takes me about 30 minutes to get through. Which is enough to get me in the flow, but much longer and I start making to many mistakes.
Small - I spend less time on toilet that way
But then you need to go to the toilet more often 
Small! I start to get frowny if I have 15 reviews piled up, and if I get more than 25 I do those 25 and wait an hour before doing the next 25 etc.
Iām not a big fan of piles smaller than 5 either, though. XD
I do my reviews in other places too. It is just that I cannot finish my business until i finish my pile (of reviews, of course)
I have one new method of doing reviews in afternoon: 25 reviews - round of gwent, repeat until done. After that 10 lesson - round of gwent.
I do the same with World of warcraft 
How do you control your level up time?
jprspereira does a pretty good summary here of how he controls level up time:
https://community.wanikani.com/t/wanikani-is-too-slow-and-the-radicals-are-useless-also-why-cant-i-just-level-up-in-one-day-instead-of-7/27040/51?u=gojarappe&source_topic_id=26099This is getting so shared I might have to write a better version 
Haha, get to work.
Also, on the topic of this thread, I prefer no reviews, a nap, and some ice cream. But since that is not feasible for learning Japanese, in the real world, I donāt really care either way. If there is a big pile, I break it into small piles of 50 reviews and conquer it slowly and feel satisfied. If there is a small pile, I conquer it quickly and am happy, but I realize there will be another big pile later so no need to be too happy.
Mainly by using the reorder script. For the first 20 levels I wanted to level up as fast as possible (also because I already knew about 400 kanji) so I did radicals first, then kanji, then vocab. When I hit L21 I was moving houses so I took a whole month where I didnāt do any lessons, only reviews. Simply not doing new lessons for a while really takes the pressure off. After L20 I changed my strategy to radicals + vocab first, then kanji last so I wonāt level up too fast with a batch of unguruād vocab piling up. I took another long break from lessons when I hit level 30. I donāt want to risk burning out, and at level 30 youāve learned 1000 kanji with is a pretty solid basis for reading simple texts.
I disagree, a nap is good for learning japanese 
awww god, gimme the big ones, for breakfast, with a cup of tea, while my pajama-smell hovers through the house and leaves behind nothing but rot and despair! uowou
Definitely smaller. I do my reviews as they come in throughout the day so I usually end up with 60-70 at most when I wake up.
I think the rot and despair kanji are on later levelsā¦
Which means only then I can get dressed and collect them? 
I have just finished clearing over 300 reviews after not having time to really get on top of themā¦ never again, small review blocks from now onā¦ my brain hurts.
I feel exactly the same. So long as the pile doesnāt get to be more than 200, I prefer doing one big pile a day than coming back and doing a bunch of little ones.
I personally like small reviews. I need to beat each kanji in my head for like 10mins each for me to actually learn it.
Definitely smaller. Around 50 I guess.
When thereās too much of them, I start loosing patience and focus midway through and start making a lot of mistakes.
On the other hand, when is a small amount I can focus better on what Iām doing. Plus, itās quicker, so itās easier to have time to do them.