It's something that I've been thinking about a lot lately, especially after reading "A company of one". That it's possible to make a good living with friends and not be the next X or Y hypergrowth company.
For some context, I am currently working for one of the hottest startups in the world (not hyperbole, we have the metrics to back it up), and I have been here long enough to remember when we could all fit in a small room.
The first 2 years were a dream, this last year has been pretty terrible, and coincidently, is when we started our crazy rapid growth.
It went from a place where you felt like you were working with your friends, and could have great conversations/humour and learn, to politics, arguments, poorly defined scopes on projects, process for the sake of process, or no process at all, but not knowing whom to ask, and not being empowered enough to sort it out yourself.
I realized, and I think I kind of knew this previously, that my happiest work was when I was working with a small team of smart people who could relate to each other. Basically, going to work with my friends.
I think after the IPO, it will be time to leave and find/start something similar to what you are doing.