Should I make separate notes for UPSC Prelims and Mains or integrated ones?

You should prioritize integrated notes, as nearly 80% of the UPSC syllabus overlaps between the Prelims and Mains. Treating these stages as separate leads to redundant effort and prevents you from developing the deep, interconnected understanding required for the exam.

The most effective strategy is the "Mains-First" approach. During the first several months of preparation, focus on creating comprehensive notes that cover both factual data and analytical depth. It is far easier to extract specific facts for the Prelims from a detailed Mains note than it is to build complex arguments from a simple list of facts.
Structure your notes using a layered format:

Layer 1: Core facts, Articles, and dates for the Prelims.
Layer 2: Arguments, challenges, and Supreme Court judgments for the Mains.
Layer 3: Data points and committee recommendations for Value Addition.

In the final 90 days before the Preliminary exam, you can simply "filter" these notes, ignoring the analytical layers to focus strictly on memorizing facts and figures. This integrated method ensures you are prepared for both stages simultaneously without duplicating your workload.