Most OnePlus flagship devices support updates for 4 generations of Android and security patches for 5 years. So far for security patches only Google Pixel is given monthly under Pixel Feature Drop. OnePlus only provides updates every 3 months, but this will change as they want users to get the best out of OxygenOS.
Starting this month (August), OnePlus 8 and above devices including OnePlus Pad, OnePlus 12 and OnePlus Open will start receiving monthly updates. It will still be distributed OTA but the download and installation sizes will be smaller. OnePlus will provide frequent bug patches, instead of waiting and gathering in updates every 3 months. OnePlus expects the U120P01 and U120P02 updates to be received by all users including the OnePlus Nord by September 6.
OnePlus' strategy is slightly different with the Pixel Feature Drop, as Google not only patches bugs and provides security patches but – but also provides new features and functionality. Maybe in the future this will change. At the same time, OnePlus will not provide updates for 7 years like Google and Samsung.