A common timeline for preparing for the UPSC Civil Services Examination is approximately 12 to 18 months. This timeline may vary based on an aspirant's prior knowledge and study habits. The preparation process can be divided into phases: initial foundation building, rigorous revision, and final mock tests. During the first six months, candidates should focus on completing the syllabus and building conceptual clarity. The next phase should prioritize revision, practice, and current affairs integration, culminating in a final review ahead of the examination dates.