I know a couple of kids who took six APs in either their junior or senior year. They did very well in them, dealt with the pressure, although it wasn’t particularly satisfying. It is a very demanding course load.
Here’s the thing, though… neither one got into tippy top schools: their first, second, and third choices. Their families were stunned, the kids were crushed. They got into very, very good schools… schools I would be proud to send my daughter to (both ended up at selective programs at state flagships going for pre-med). But they didn’t get into the T30s they wanted, even with straight A’s in all those APs, near-perfect SAT scores, and taking no lunch period… the sacrifices.
It worked out for them, they’re happy where they are. But they probably would have ended up in the same place with one or two fewer APs and a little more time spent on things they enjoy more than studying.
So think carefully why you want to do this. Maybe you need to save money in college, and getting credit for those APs will help you. That’s understandable. At the end of the day, though, if you are just trying to impress your college of choice, you might more effectively do so by taking fewer AP classes but achieving great things or being very impactful in your ECs.
BTW, I think it is GREAT that you are planning your four years of high school as a freshman. DD was able to take advantage of several opportunities she otherwise would have missed had she not done that. She has friends missing out on classes they would have loved to take simply because they didn’t look ahead (didn’t bother flipping through the curriculum guide), didn’t realize what was available until it was too late to fit in prerequisites for those classes (her school doesn’t have many elective spots as gym is required for four years as well as some other classes). While not everything went according to plan for DD, having a framework in place made it easier to make decisions on alternate plans when the unexpected happened. Kudos to you for thinking ahead!