It is indeed subjective. If you would like to make gains by slowly expanding you can try 30 minutes of a wiring field and you should be fine, especially if it’s a subtle field like social bonder.
But if you would rather increase gains, no one is stopping you from playing until you reach your unique and individual limit.
I know that personally, as soon as I found out that the autism overgrowth from the Manhattan Method was normal, I began playing as high as possible. I think within a month I was already on my first 10-hour day with fields that caused brain pain like Mathematical Madness lol.
You don’t have to worry much, I would just listen to my body. If your plan is to raise as high as possible, then continuously raise the bar for yourself at a comfortable level (Which you should be able to pinpoint mentally.) and then work from there.
See you already have a good amount of endurance and you played Pboy to cut any potential axon overgrowth, etc.
I think if you continued to expand upon it and try out more you’d be completely fine. That was the case with all of my friends, including me.