Early retirement has a totally different meaning than retiring at an old age. At old age, you think of covering your medical expenses, sufficient enough money to take of your needs for food,clothing and shelter till your very soon to happen biological death. Besides you don't really have the energy and enthusiasm to enjoy the same things somebody young does.
At an younger age retirement has a different meaning. It means traveling, riding your motor cycle in rallies to far off places. Roaming around the country trying out different sort of food, Playing video games and your favorite instrument during Sunday afternoons.
In order to do all this you need a supply of money that isn't mediocre by measure. In this case, even if you have $900K (I don't know if this is sufficient in the US, I'm from India) that may not be sufficient to live a life of even mediocre decent luxury.
If the idea is to live hand to mouth the rest of ones life, then retiring with $900K at 35 isn't bad idea. Other wise,... One has no option but to get back to work.
