Bravo 73 has it one - whether you like it or not, if you're being paid to fly it, you're being paid to mind it too! Overnight parking or other parking situations have to be considered in the preparation for the flight in the context of any risk of damage to the machine.
Private owners operating their own aircraft have to make the decision for themselves on a case by case basis. But the old rule "where there is a doubt, then there is no doubt" should apply in all cases.