Or just be good at kicking ass
Working full time and working as a part time CTO has drawbacks, which I've covered. That's played out. A lot of blogs talk about how hard it is to work all these hours and how you give up this and that. Those people are chumps. There's a hell of a lot of exciting stuff that goes on, too. For example: Dinner meetings (read: get drunk and scribble notes on napkins). Yeah, you still go out to dinner and yes, you probably wouldn't be taking any notes, but it feels like I'm getting paid to have my CEO buy me dinner and drown me in beer. It could be worse.
Get autographs
Second, and this one is important, you meet all kinds of seriously interesting and awesome people. A lot of people on the scene are jokers, but there are some seriously insanely smart, driven, attractive (less important), successful people. Cincinnati alone is crammed with the varsity squad of the midwest. Just being able to brush shoulders with people who are not only smarter, but a hell of a lot more accomplished than me (and sometimes younger), is humbling and exhilarating. Side note: one day people are going to say that about me.
John the Builder
Thirdly, I create some ridiculous shit. When I'm working crazy hours and just fall into that weird zone of productivity, I impress myself. I've spent a few thousand hours developing in Python/Django and it definitely gets easier, trust me. I plan on open sourcing a lot of cool functionality once everything is launched and cleaned up. I think being a lead developer on any large-scale project takes just as much creativity as designing it. Plus more logic! Less women though, sadly.
In closing
Working on any side project, especially a startup with a raging deadline and a crazy CEO, will lead you down avenues you never imagined to meet people you never thought you'd know and to create things you never thought you would. It's just awesome. I grow every day. I think expanding your skills, building strong ideas and opinions, and forging new relationships are what it's all about. Oh, and the hope that one day you'll get a big fat check doesn't hurt either.