This is great advice. Going through the application is itself a great exercise in developing our products and pitches. There are so many paths to success, we just have to keep taking them as they come, whether they be in the form of organizations like Y-Combinator or serendipity... it's almost romantic, don't ya think?
i've been doing this for a little over 3 years now. during grad school i wrote the beta version of my software when i wasn't working on my thesis. now i work during the bulk of my non-day-job time, but i make sure to have leisure time, too.
i think the danger of this lifestyle is the risk of not getting things accomplished in a timely manner. if we spread ourselves too thin we end up with our hands in a bunch of half-full pots.
nonetheless, kudos for the stamina. we have 24 hours every day to use how we see fit. 8 hours for sleep is a given, 8 hours for work is another (almost) given, and what we do with the other 8 hours is the difference between mediocrity and success.