You say that as if it was a bad thing.
People need fun. It makes them feel better. People who feel better work better and are more productive. I wouldn't be surprised at all to find out that an extra day of fun makes the four days more productive than the five days of work.
Hours worked is a lousy way to measure the contribution a person makes to the organisation.
Maybe you need to get out of the office more, bud.
What I think happened here is that you did a number of things right which affords you this flexibility in hours. I would say the real story is that you made something of value vs the free-but-pointless model we read about much more often these days. You built a business around something valuable with a relatively high price point that makes it less of a victim of the kind of scalability issues that "general public" web based services are dealing with.
I think the bigger take away would be: If you make something awesome for the general public that millions of people will be using all day long, plan to work seven days a week 'round the clock and there's no guarantee you'll ever see a penny. If you come up with something valuable that people would be willing to pay $25-$50 a month for, your life will be much, much more enjoyable and you might actually get to watch your kids grow up and/or have some time left for your hobbies.
This proves it's possible, even when you're young, stressed and unprofitable.