Also, I've seen that 4-5 years is about how much time engineers are willing to put into a startup company before they want some kind of a cash out : liquidity : burn your options in a barrel at burning man situation. If you think about the expected half-life of a silicon valley engineering career, you can probably do 2 or 3 of those before you are burned out entirely or prefer to work at a non insane company. Founders are probably not as aware of this because they naturally are 100% invested, but you have to surround yourself with quality employees who won't put up with your bullshit forever.