John Piper answers the question of whether pastors should get PhDs. You can find the transcript here.

I was just discussing at length with a fellow pastor friend who was considering doing his PhD in NT in UK. For myself, the thought has always been at the back of my mind, firstly as I have always enjoyed academia, and absolutely treasured and thoroughly enjoyed my M.Div studies @ SBC. Secondly, as part of future ministry, it would be in line with God’s leading me in the direction of focusing and developing in the area of teaching, in the context of the local church, the mission field, and perhaps one day, in seminaries. However, I know that pursuing a PhD for me will not be something in the near future, and I have decided in my heart that I would only pursue this if and only if God makes it clear for me to, both in direction/leading, but also in providing and opening opportunities for us in the future. Also, I would only pursue it if it is absolutely vital for ministry, not for personal pursuit or gain, both in knowledge and credentials. If I was to go ahead, the programs that I would consider would be not so much pure OT/NT studies, but rather something along the lines of pastoral theology, leadership and ministry. Some would recommend a D.Min instead, but somehow, I would also like the challenge to commit to the PhD research and thesis component. I agree with Piper, however, that I would not want to be in a program where I spend most of my time just reading junk. It would have to be a good balance of actually learning the Bible and theology, spiritual formation (character, mentoring, spirituality), and ministry/outreach (missions, counselling, leadership, evangelism, etc).