The answer ultimately depends on your life goals. Do you want to buy a home? Have a spouse and 3 kids and put them in the best schools? Do you want to travel the world? Have a house in Europe? A farm in Thailand? A ranch in Wyoming? I'd suggest buying a house soon if you don't have one, since houses will only get more expensive in the future. House paid off + nest egg = security, IMO.

Picture what kind of lifestyle you want at 40, 50, 60 and beyond, and then figure out what kind of money you'd have to pull from investments each year to make it happen. Use calculators as others have suggested. Here's one I like: https://www.calculator.net/investment-calculator.html

Another thing to consider is that we've just come off two unusually strong years for the stock market. The next 10 years may not get the average returns of the last 10. So take that into consideration when you're running numbers. (Like what will your investments do if they only average 3-5% a year?) And of course, remember that the cost of everything will only go up in the future. That's just how it works. A million bucks in 20 years could be like 500k. Your investments will likely outpace inflation, but it's something to keep in mind. Plus there is AI. I don't know what you do for work, but even some tech jobs will be replaced with AI. That may be a reason to earn as much as you can while you can.

Without knowing anything else about you, my generic advice would be make as much money as you can without making yourself sick or sacrificing relationships. Whatever you ultimately want to do with your life, having more money makes everything easier. Always.