I'm 34. I was more worried about the age mattering to me than to the school. Or more accurately, the responsibilities I have rather than the age. I have a mortgage and an 18 month old son. I applied to a PhD program understanding I'd have to quit my job. And I'm finally making good money (but the work isn't meaningful to me). Going from 'good money' to a $16k / year stipend is something I can't just jump into given my commitments. Luckily my wife has a good, stable job. They pay teachers well here in CT. So we can probably make this work, but my choice to go back to school will require sacrifices from my family.
I found out I got accepted to my program of choice today. Which is f-ing awesome, but it makes all the money stuff real now. Had I had my epiphanies when I was 25 I would not have this conflict. For me, this is why age is relevant.