What I mean is, say we have a whole batch of reviews of 90, but I don’t feel like doing 90 reviews at once. So what if I want to spread these 90 reviews out over 3 times that day? So one batch of 30 in the morning, one batch iof 30 in the midday, one batch of 30 in the evening?
So basically, a usrscript that takes a custom amount of elements from the review pile and only presents them, and not the rest in that one sitting.
Is there such a user script?
You can click the clock on the left (under the input box) and after 10 completed reviews it stops the session.
I imagine there are userscripts but for the interim you can just use that, just need to reload the review page after every 10 reviews.
There’s a script here called Review Queue Sizer. I’ve not used it but it sounds to me what you’re after
This is exactly what I wanted, thank you. If it was possible to somehow say “older reviews first” then it would be perfect, but that alone is great as well.
You can do this with reorder omega using an “overdue” sort action and a “first” filter
You can do 20 and then hit wrap up. 
Doing just 20 out of 90 means doing essentially 50 reviews, because a review only counts as “finished” if you get meaning and reading right, which come at random intervalls. However the solution to this was already provided, thanks to a handy user script.
FYI, the implementation isn’t completely random. Here’s a recent post from kumirei that covers it:
Hmm?
Afair, the number of active review items is 10.
(Oh, it was mentioned above)