Consider that the vast majority (something like 9/10) of companies fail within 2-3 years. If you're not willing to deal with failures, chances are you'll stop trying long before you get to 12. If you deal with the odds, you keep going as long as you get something out of it

Also, even companies that "fall flat" may be worth it. For my part, a large part of my current salary is down to my experience and contacts from my various startups. And each one of them have been fun for the most part.