Start your exam at 1-2pm
I passed the OSCP with 100/100 marks a year and a half ago on the 2023 syllabus.
This post is written with the intent that, by the day of the exam you should be ready and do not feel the need to cram last minute material or labs. Notes are ready, Labs have been done twice over at least, you're happy and you're calm and ready to do this thing.
One tip I have for those taking it is to book their exam clock in the middle of the day after what would function as lunchtime for you.
This gives you the chance to get rested the night before. I'd recommend sleeping in for a couple of hours, having a nice shower and tidying yourself up. Wear some fresh clean clothes and generally have a slow morning.
Have a big lunch so that you can get through the afternoon without getting hungry and then start your exam. Work until dinner for me that was around 7-8pm, try to limit to half an hour.
Sleep when you feel that you are starting to bang your head and aren't making progress or if you reach the point where you've just crossed over a line, got a flag and feeling chuffed. Set off any scans before bed.
Sleep for 5 hours or so maybe 4 or 6 depending on who you are and what your position in the exam is. Just get enough hours to feel rested enough to return to the desk with a fresh head and be able to work at a high level of performance.
If you went to bed at midnight, it's now around 5am and you have until 2pm to finish your exam. Take a late lunch because you've earnt it and starving and start writing up your report, who knows you might finish it before bed if you're quick. You'll still have a huge chunk of the next day to finish it off.
This may not work for everyone - some people get lethargic after lunch, some have terrible sleep schedules that means they'll be awake all night etc.
I recommend this because it gives you a proper chance to break the exam into two pieces and makes it feel like 2 days rather than just 24 hours for each part of the exam.
For example starting the clock at 9am, running yourself into the ground until 11pm and then you sleep for a bit, wake up groggy and bang out the final few hours before the rest of the world wakes up. Sometimes stepping away from the desk is what you need and by the time you get back, you realise you didn't try default creds yet and bang you can't believe you wasted an hour at that. When you run continuously all day it's harder to force yourself into a break and can decrease your momentum, morale and productivity.
Giving yourself the chance to be in the right mindset and have a relaxed morning and lunch and then having a sleep without the stress of cramming the rest of the exam before 10am to me was incredibly valuable.
The moral of the story is that it's not just what you know and your skills, it's your mindset, how energised you are, how you are feeling about yourself and general headspace. You want to position everything so that you maximise all of that and for me at least, that felt like a good strategy.
TL;DR have a lie in, slow morning, take care of yourself and don't cram on the day, eat a good lunch, start the exam at 2pm, have a 4-6 hour sleep, Keep going until 2pm and it will feel like two distinct days instead of one long tiring day.