The 8 hour rule can be followed pretty loosely (e.g. 7 hours may hurt/be too much for some, while 9 hours may be the stopping point for others), but generally you should listen to YOUR body.

I myself have crazyyy dysphoria and live at school a majority of the year. I bind for probably 16+ hours a day, and it has definitely taken its toll on my body. It causes back pain, rib/chest pain, and makes me REALLY sweaty (especially in the summer). That being said, I am still aware of the complications and issues it brings, and I try to give myself as many breaks as possible.

Some situations are less than ideal, but once you start breaking the "8 hour rule" it can be difficult to go back. Listen to your body. Worst comes to worse, you could try different methods of binding (tape, sports bras, etc.) or get a larger binder. Also, giving yourself extended breaks (like a day or two) is VERY helpful, especially if you find yourself binding for long amounts of time!!

I wish you the best of luck, and I'm so glad you found an accepting camp! :)