I've used a CTek conditioner since I've had the car (7 years) and leave it on permanently unless I know that I'm definitely going to drive it within a few days, that's the main purpose of it as the battery voltage drops sufficiently to make starting a struggle after a couple of weeks.
I am on the other hand paranoid about not leaving any other phone, pad, etc chargers plugged in unattended as they are apparently (along with dishwashers and washer/dryers) the main cause of house fires now.
