I didn't write much until I turned 40. Up until then I felt constrained by a sense of the discipline of New Testament studies and a sense of the ruling elite in theology and biblical studies. -- N. T. Wright
A majority of young people seem to develop mental arteriosclerosis forty years before they get the physical kind. Another question: why do some people remain open and elastic into extreme old age, whereas others become rigid and unproductive before they're fifty?