As always, Murphy's Law seems to prevail no matter how well we prepare for any circumstance.

Call me paranoid, but when I put my car in the garage for short or extended naps I usually follow this process:

~ I rarely activate the Alarm, and never lock the doors, as it's a locked garage.
~ I always crack both windows and leave them down about 2 inches.
~ I always hook up the Battery Tender.

I know that this is not the safest, or possibly the best was to close things up, but in my situation, the garage is attached to my house, and not remote storage. So even in the dead of Winter, it rarely goes more than 3 or 4 weeks where I don't touch the car (or at least turn it over and move it to reduce flat spots on tires)...