$3M is a lot, typically the rule of thumb is that you need 25 years worth of living expenses to be financially independent. That means you expect to spend $120k yearly? That's up to you of course but that fits exactly in what I said about choosing how much you spend. My monthly expenses are currently < $1500 per month (for 2 people, in Sweden), and I think it's more likely that I will taper off working (work fewer hours, more fun but lower paying jobs) than that I will stop working altogether. That means $300-400k would probably be enough to provide a significant level of freedom especially once my girlfriend graduates and has an income as well.

My salary is far from an SF salary and I do work full-time but I find my work quite fulfilling. If it weren't I wouldn't have much difficulty finding work with more freedom for e.g. part-time employment.