Impossible to know bro, but at 500mg a day you get into the danger of metabolite poisoning. Kills your liver. So the most I have ever taken in a sitting was 500mg. I used to love demerol, but after oxy I won't go back. When I was in the ICU post op in hospital though my resident nurse refused to give me oxy so I had to settle for 50mg IM demerol every 6 hours. Was great for 3 of those 6 hours. Then they talked about changing me over to 50mg oral. I told them if I was going oral I wanted 100mg due to the first pass effect, which apparently no nurse or doctor has ever heard of. Anyhow I am rambling.
Only you can decide your own tolerance levels, but 500mg is the point at which you risk liver damage.