> Sorry if this is off-topic (and maybe a bit personal), but as a recent graduate, I'm not sure what I would do with all that extra money. What do you (or most people) generally spend it on? I make less than that, but if I didn't have student loans, I wouldn't know what to do with it besides leave it in the bank.
Saving it (in an index fund rather than a bank) is an excellent thing to do with it. Keep living like a college student (or even a fair bit better than that), and save the rest, and you'll be able to retire in your mid-to-late 30s.
Resist the inclination to expand your expenses to match your income; it doesn't actually make you any happier, long-term. (Many different studies have confirmed this: increasing your level of spending tends to give you a short-term burst of happiness followed by a return to the baseline; it doesn't permanently raise your baseline.)
You don't necessarily have to retire early. If you prefer, keep working past that point as long as you're enjoying yourself. You'll be able to have a lot more flexibility in your work, and later in your career you'll be well into the territory of "start your own charitable foundation" or "don't bother raising a series A".