Take the job if you feel it is your dream job.
I lived in Cambridge and worked in Dover, NH for five years (I have now lived in Florida for seven). It was approximately 75 miles away and the evening commute always took about 15 minutes longer than in the morning. I am from NH so I didn't want to move back and I also didn't have family at home to worry about.
If you are entrenched in Dorchester, you can make it work; if there is any way you can transition even a half-hour closer to your job at some point, then all the easier. If it just doesn't work out, well, you can always go back to doing what you are doing now. It's important to take chances in life and you would probably regret passing this one up.