Why do my Bluetooth devices keep disconnecting and need to be paired again?

Why does my Windows 11 PC randomly disconnect Bluetooth headphones and mouse, and why do they only reconnect after I remove and re-pair them? Why does it happen more often when I'm using both at the same time, and why does restarting the Bluetooth service only help for a few minutes?

Could this be caused by a power management setting, a driver conflict, or a problem with the Bluetooth adapter itself? And is there a permanent fix that stops the disconnects without replacing the hardware?