I found a few things of interest when thinking about a doctoral program: http://www.phd-survey.org/advice/advice.htm and http://survey.nagps.org/ Be a smart consumer and don't fall in love with it (the program).
I had a zest and a fire for undergraduate and graduate studies. The inner fire burned brightly!!! But I now have no inner fire for doctoral studies. Thus, I am now "going for the money."
I agree with the history doctoral students. I want it because I have wanted it for over 30 years. I want to tell the story of my research. I want it because the fire in my belly wont go out. I do know there arent many jobs in history. That is why I have my MLS. I am perfectly willing to work at NASA for years. I am also paying for my tuition out of pocket ( By teaching at Devry University). I would NEVER take a loan out to pay for my PhD in history. It will not pay itself off, at least not in my mind. I am doing this to finish. I learned awhile back that jobs are few and far between. I do agree that you should be older before starting a PhD program in history. Just my opinion.
I am so engrossed in my doctoral research - it consumes me day and night!!! I love it, and can't wait to do further research in the area. Cheers, George