Sorry to repeat myself so often, but in the Preaching class I try to encourage preachers to: (1) read the whole Bible devotionally once a year, cover to cover, or at least once every two years (if they use the Daily Lectionary), (2) to consider the whole canon fair game—at least potentially revelatory—for preaching (so I require a sermon that comes from beyond the RCL), and in both the Reformed Worship and the Psalms classes, I stress Calvin's view of the Psalter as "the anatomy of the soul." "Be ye perfect," I suggest, means: "Be well-rounded, fully formed, complete." So the Bible reading plan I suggest actually includes reading the Psalter, not just once, but seven times per year, in a fifty-day cycle.
In preaching class, I also encourage students to "make friends with" or get to know the works of a few great preachers and/or theologians (the sorts of names we were sharing at a recent faculty meeting), and to eventually find one whose entire output (or as much as possible) they would like to read and even develop some expertise in, so that they might share it with the church and perhaps do some eventual graduate work.
In the worship classes, but esp. in Reformed Worship, I tell them about my excavations into the 1520s — big surprise, I know — in order to let them know that our history is rich, our family is vast, but close-knit at the same time, and there is a lot (!) of buried treasure—forgotten, untouched, untranslated, never before voiced in English—in the church's attic; this, in addition to a similar point made (above) about the treasure field of scripture.
In short, I ask them to think about not only planning their next sermon, or even just planning a years's worth of sermons, but envisioning a lifetime of sermons in the years they hope to have remaining. That is a poignant point for most preachers to consider, but we only have so much time and so many sermons in us. How will you approach covering the territory —the whole of the preacher's book — with what time you are given?