I'm running Armbian 20.08.1 (Ubuntu) in NanoPi NEO3, and after running sbc-bench,sh benchmark, the temperature does not revert to the idle temperature for several hours until exactly 4am.
The system was idle all that time, until a small CPU usage spike at 4am. That's because it rebooted at that time, maybe due to a short power failure.
So what confuses me a lot is why the idle temperature will get back to around 60C only after a reboot. 11 hours of idle time would not do it, but a simple reboot would magically drop the temperature by close to 15C.