If you have "quite a tolerance", the doses you stated in the OP will be fine. Hell, the first opiate I ever took was codeine, and I used 300 mg for my first time. Not the brightest idea but I didn't notice any suppression of breath. Further, the LD50 for codeine is quite high. I'm unsure of the level right now but you can Google "LD 50 for codeine" and find it. I believe it was above the 800 mg mark. It really does take A LOT of codeine to OD and die from ...