Many use a strict schedule for reviewing, that will give you reviews at specific times of the day. Maybe try it yourself?
In any case, for planning it, try to consider the SRS-timings:
and reading this helpful post:
It really contains all you need to know about how to manipulate and control the reviewing process.
Personally, i did like you, reviewed at various points in the day. Though never during the night. There is simply no need to do any reviews when you can sleep. Don’t do WK slavishly like that. Just do reviews that have accumulated when you wake up!
But, for others, it’s better to make reviewing dedicated time-slots that can work within their study/work/life-schedule overall. That’s for you do decide. 
Good luck with your studies!
Edit: for example my schedule looks like this now, since I never ever do reviews before I wake up, and now I also don’t do them after a certain time of day, when I just wanna relax and watch anime etc.
Basically, the Apprentice levels have hours between the SRS-stages. But later on we’re talking weeks, months and so, which means the reviews come back the same hour, just a week later for example. If you simply stop doing any reviews in the middle of the night, there will be no reviews in the middle of the night.
Basically, I only do it in the morning and maybe at lunch. Or I’ve accumulated reviews to do, which can be done whenever.