A.W. Tozer emphasizes the importance of variety in spiritual practices to avoid monotony, suggesting that even the most devoted souls can become stagnant if they do not occasionally shift their focus. He references Von Hugel's idea of 'neutral cost' in prayer, advocating for breaks from spiritual exercises to engage in simple, earthly activities like walking or gardening. Tozer illustrates this with the Israelites' journey in the wilderness, highlighting that constant movement was essential for their growth. He notes that great Christians evolved over time, requiring different spiritual exercises at various stages of their lives to maintain their spiritual vitality.