20% lets you have a better "lifestyle" and 10% is going to make you pinch the pennies a bit.

But if someone with 100k salary puts 15k away starting age 25 to 65 will net you 5 million+ in retirement... which should be more than plenty for anyone to live off for 30+ years EXTREMELY comfortably. With hopefully no house payment and other big expenses you should be able to take quite a few awesome vacations a year and do whatever you want, really.

You can essentially just withdraw $250,000 a year and never touch the principal.