Its very, very, VERY hard to keep such a company culture when you grow company big time.

You would effectively have to have people dedicated simply to this task, with massive managerial powers checking all management decisions and keep reminding all folks to stick to them (I can't imagine any other way). Its not only about things on paper like benefits and working hours, but overall company culture, agility to change and corner cases. If you manage that, kudos to you, but you are rather an exception.

I've seen it first hand - an amazing, startup-like company, growing super fast, and culture suffered.