Interesting - I guess there is some sort of balance there, given the radical biochemistry that is seen with Mitochondria. “The more [mitochondria] the merrier” …?
Further, if the mitochondria is being asked to make more ATP than it can aerobically, then it will skip the final respiratory step and respire without oxygen (anaerobically). This causes a build up of lactate in the cells that is not tolerated above a certain level, I believe due to it raising acidity levels in the cell.
You’ll often hear athletes and coaches talk about lactate threshold and Functional Threshold Power (FTP). This is all to do with mitochondria function.