> Not in my experience. It's possible to get the equivalent of a bachelors and masters in math within two year

Seriously.

In fact, most people who learn this math learn it in a period of 2-3 years. Far from being impossible, learning this math in a few years is normal. It's not even a full time job. Most people learn all this math while also doing other classes and school stuff. Even a very dedicated math major probably only spends 20-25 hours a week actually studying math. I'm not sure much more than that is sustainable for most people anyway.

Now, I'll grant, this is going to be a lot harder to do without the structure of well thought out syllabi and lectures, but it's certainly manageable.