When to stop pumping?

Moe

Whenever I pump, my milk just will not stop. I know you're suppose to pump until it stops, 5min after the last drip, etc etc but mine just doesn't stop and it takes so much time that I dont have to feel like I've emptied them enough. Like 45min to an hour. I have multiple let downs per session, hand express, and more just keeps squirting out. If I take a break for a couple minutes and pump again it squirts out like I never even started and by the time I'm done (aka give up) I have like 300-350ml. Weird problem to have but I can't keep spending an hour at a time pumping, but my boobs just won't empty. What do I do?!