It's less about that than about tangible business milestones that need to be achieved. There are two simple ones: what's your revenue today and what's it going to be tomorrow, and what's the delta between those? What's your growth rate and what is the revenue that you're at?
In the venture capital industry, there are clearly delineated milestones between stages, and there are clear goal posts, if you will, or brackets, around what metrics you need to have in order to deserve the next round of funding. That's how we do it.