"You have more free time now than you probably ever will again."
I haven't found that to be the case. I have much more time available to work on my own projects than I did in college. Perhaps not in absolute terms, but in terms of usable get-code-out-there blocks.
In college, I found that homework always got Parkinson's-Lawed so it took up all my available time. Either I was actively doing homework, or I was procrastinating on homework and couldn't justify working on other productive projects instead. Plus, available time in college tends to get broken up into 1-2 hour blocks between classes, after activities, before dinner, while waiting for friends to go out to a party, etc.
Now that I'm working, I have significantly less actual free time, but everything I have is mine. There's no work to take home, nothing hanging over my head when I'm not at work. And it's generally in large chunks, too. It does kinda suck not having a social life, but it does leave decent-sized blocks available for a startup.