In my experience the worst start ups don't hit the skids fast. They kind of keep bumping along, often for years. Neither growing much, nor dying, nor making much money, nor losing enough to go out of business. I even co-founded one of these a few years ago. If you're in one of these my advice is to recognise it and quit.
Even worse: they succeed wildly, to the extent they never need funding again after a series C, buy out the VC's, and stay private. This is roughly what I'm expecting from one of the startups I worked at. I already know they'll never need to take another dime in funding, so I'm just waiting for them to tell me how my shares are going to become worthless.
