My point here was (I don't know much about chemistry, but I'm assuming it's similar), physics in a high school classroom is very different from physics at a university level, which is different from physics at a post-graduate level. I don't mean to question your desire to continue studying these things, not at all, but simply to state that being so specific about what you want to do (double phd, and you know the university!) when temporally you are so far away from that seems a stretch. If you're a freshman right now, that means you're ~15? When you'll be starting a phd is 8 years from now, that's over half the time you've been alive! I'm just saying, things change a lot, and while it's (very) important to keep goals in mind, I think being too specific can be limiting in a lot of ways.
Haha, no not at all, you misunderstand. It's just not exactly an easy lifestyle, especially if during that stage of your life you start to think about starting a family and whatnot. If you have fellow friends from university, at that point they will probably be making salaries 2,3,4x yours, and so you can see why this might be difficult. Money doesn't often seem that important, but again just something to think about. (The situation is the same going to graduate school in general, but doing a phd twice makes it [likely more than] twice as prominent).
Just things to think about, advice coming from someone who's already done (essentially) what your next 8 years look like.