Gemini 2.5 Pro's consistent 5-chapter increment may reflect context-window optimization — 5 chapters (likely 2,500-5,000 words) fits within a single context window for drafting — after 5 chapters, the context window fills and consolidation is needed to clear space — the 4-minute interval between consolidations suggests each 5-chapter block takes approximately 4 minutes to draft — at this rate (5 chapters per 4 minutes = 75 chapters per hour), Gemini 2.5 Pro could theoretically produce 600+ chapters in an 8-hour workday — actual observed rate is lower (35 planned over ~2 hours = ~17.5/hour) because consolidations and chat monitoring consume time between writing blocks