I don't know what you mean by "self-sufficient". Neglect a stable company and it will go out of business. The technology market is always changing and you have to keep an eye on your competitors and new technologies.

Sustaining a business over the years and making it through the ups and downs of the economy can be an extremely interesting challenge.

Yes, but to some "sustaining" is very very boring.

Maybe the key is that rather than just "sustain" you have to keep building and growing.

Why are people talking like 37signals is in a sustaining mode? They regularly release new products and significant new features for existing products. I'm pretty sure the people there still get the sense that they're creating something new.

One of the things I've seen is that the business becomes like an extended family -- that the founders get emotionally wrapped up in the people. It's not only the challenge of the work anymore, it's the commitment everyone has made to each other. They stop being at work all the time because they're solving world hunger and start being at work all the time because -- it's home.

Doesn't happen all the time, but I've seen it more than once. I'm sure there are other scenarios that could play out.