The cool thing about your liver is that if you are kind to it, unlike many other organs, it can self-repair. Trust me, I'd be dead if the damage was cumulative.
The uncool thing, as has already been mentioned, is that there are no instant symptoms. I remember seeing a fly ont wall documentary once......this geezer necked like 50 paracetamol to kill himself. He woke up in hossy, and was all glad it "hadn't worked", full of love of life....until the doctor told him he had exactly 3 days to live. He turned yellow and died right on cue.
I must confess I've gone over the safe dose a few times in throes of agony (before the doc gave me trammadol), but always took it easy thereafter to give my inerds a chance to heal.....or I'd be toast.
I actually checked safe doses online, strangely, while the dosage on a box of paracetamol is the exact deadly dose, Ibuprofen can actually be necked in twice the stated quantity