Stop a little earlier, take bigger breaks (if time permits, it's ok if it even goes soft between sessions), and PLENTY of hydration. I'd advise keeping some water by you, and drinking it whenever you stop before PONR. It'll even help with bigger loads/precum, if you're into that.
Another thing could be changing up the type of stimulation. For me, stroking up and down the whole length quickly can be super stimulating, so when I'm getting close, I'll switch to just massaging the balls, or only rubbing one part of my dick (just the tip, lower shaft, bottom of shaft, etc.)