We have just had one in with a battery drain, The customer had just bought the car and had a towbar fitted. initially the drain was about 2 amps and it never went to sleep, We disconnected the radio and got it down to 0.7 amps. So a used radio was fitted.

It had a tow bar kit fitted and the drain would drop off if that was disconnected. So it was fitted with a relay to switch off the towbar electrics completely with the ignition off.

The customer still complained of intermittent flat battery. One of the rear door latches was faulty so we fitted a new one, We left the car overnight, started no problem, left it over the weekend turned the key.......CLUNK. ??? ( What the heck ),But then it kept starting ok for 3 days after that. ? Battery seemed ok, We put it on the ramp to check voltage at starter and connections, looked up and found an M8 bolt welded to the starter terminal and resting on the starter body causing a dead short when they key was turned. ( very lucky that it didn't cause serious damage or fire ).

The car has been fine since but it did take some sorting due to several faults but it did take a hell of a long time to go to sleep sometimes and appeared to shut down quicker if deadlocked.
I think it was about 45 minutes or so before it went to sleep after being locked or deadlocked.

H.T.H Tony.