Android is the world's leading mobile operating system, with over three billion active devices. Detecting vulnerabilities and ensuring timely patch deployment are critical to maintaining security. The Android Open Source Project (AOSP) has enhanced the transparency of security updates through Security Patch Levels. However, challenges related to update speed and availability persist. In 2022, Google reported that half of the zero-day vulnerabilities discovered in the wild were variations of vulnerabilities that had already been patched. Recent research mainly highlights delays in update distribution, often attributing them to fragmentation and focusing primarily on flagship devices or limited time-frames. Our approach takes a device-centric perspective to investigate Android update patterns, analyzing 567K security update records from 2014 to 2024, covering 904 distinct devices from six key Original Equipment Manufacturers (OEMs) across 98 countries. Our extensive analysis revealed notable differences in update release timing across OEMs, device types, and regions. Our study also examines documented vulnerabilities and weaknesses, while assessing OEM compliance with Android security guidelines. Our study shows that$\sim$89.7% of vulnerabilities on unpatched Android devices are exploitable without user interaction and with low attack complexity. We also identified delays linked to fragmentation and OEM-specific challenges, and provide actionable insights for improvement.