Different religious cultures produce different expectations about sermon length. My sense is that the average Episcopalian begins to squirm in the pew after about fifteen minutes. I was once invited to preach at an African Methodist Episcopal Church. The pastor told me that their tradition was to preach longer sermons than we Anglicans preach. I worked hard and produced a sermon of 45-minutes duration. After the service, many of the members of the congregation shook my hand and were very gracious, but several asked "Why did you stop preaching when you were just getting warmed up?"