I'm in the first year of HEP PhD program and currently learning QFT. The reason why I'm still learning QFT as a grad student even though it has been almost 9 months since I started PhD is because I started physics lately - I changed major when I was junior. I haven't studied SUSY, Supergravity, and, String theory but I want to explore all these topics. However then I expect it will take more than two years before I actually start research. Then I'm afraid that it will make PhD period too long. With these concerns, I glanced at some books dealing advanced topic, However, on the one hand, I think It will be better to concentrate on a single topic at a time and try the other after that and so on because I thought that cramming multiple things at one time will let me end up knowing nothing. I am curious how people think about this. I am considering to postpone advanced topics after the research, perhaps after getting Ph.D., try PhD again.... it may not be efficient. I will be glad to see your advice.