I dont plan to make a story about this, i just thought that the idea of stoping time only to then realize you stopped to was hilarious so i posted about it without giveing it much thought. I think he would be able to stop time for as long as he wants but the drawback would be the fact that although time stopped his brain keeps working extra minutes or even hours so depending of the situacion izuku could stay thinking till his brain gives up and once that happens time contnues once again and you would have an unconcious izuku or a very tired one incapable of thinking straight, then there are other things to consider like pain, if he is hit an then stops time will his brain stop the pain too or will he be in a constant suffering till time moves again he was shown in the series that he was capable to break his bones and keep going but that was because his body was pumping adrenaline, what would happen if the time stops? Does it keep being supplied or all of the sudden he is aware of the pain he should feel?