There is a consumer delay of about 15-20 minutes, from when you turn off the ignition or unlock the doors.
You can see this by either opening the boot and watching the light turn off or removing the key after a journey and waiting for the interior cabin lights to turn off.
I have a broken light in the glove box, the switch broke and the lamp eventually burnt out, this caused a parasitic drain till it broke.
Only noticed when I swapped the concert radio for a new unit.