The duration of the UPSC Mains examination is typically spread over five days, with each day dedicated to specific papers. Candidates sit for a total of nine papers, including compulsory papers like Indian Language, English, and four General Studies papers, along with two optional subject papers. Each paper lasts about three hours, allowing ample time to demonstrate knowledge and analytical skills. This multi-day structure is designed to adequately assess the comprehensive understanding and writing ability of candidates as per the challenging syllabus set by the UPSC.