I'm 34 years old, and I'm thinking in applying to MIT computer science PhD program with some funding. The PhD will take 6 years to complete. So, if everything turns ok, I'll end the PhD with 41-42 years old.

This reason that I'm applying is because I quit my job, and I always loved to work in academia (altough, nowadays I don't know if I want to be a university professor). I'm in a BIG dillema. Is this a feasible idea? Any suggestions? Any thoughts about that?

Are you worried that you are too old? I don't think this is an issue. I was 40 when I started my PhD. :-)

Good luck with it!

Yes, I'm worried about that, and by the fact that ending the PhD with that age does not compensate. Did you already finish your PhD? Do you have the intention to become a professor?