Am I changing jobs too often?

I am a computer science engineering student and a web applications developer in Bangalore. Over the past 6 months, I have worked for three different startups. I changed because something better always came along. As of now, I am on a contract with a social application startup which gets over in 2 weeks. The boss is looking forward to hiring me full time after the contract and I have agreed to it for now. But a close friend of mine wants me to start working with him full time on some development contracts. This new thing will be more risky as he is just starting up. To be honest, I do have some issues with my current job. I have been working for the last 15 days without a single day's leave as the project was at a very critical phase(risk of loosing investment). I have to continue college after 2 months and I won't be able to put so many hours of work every day.

My concern now is that people(those who matter: future employers or investors) may think I have no commitment. On the other hand, I am still a student and I don't think this is such a bad thing.

What do you guys think? What is your initial opinion of someone who has changed his job (not fired) too often in the recent past?