You should be able to idle your car for as long as you have gas. I've never heard of anything bad, maybe cooling is better while moving, but that is what the fans are for. The only part that might do some harm is the transmission. This normally is not an issue unless your car runs 24/7 like a cop car.
Really if there was a problem there would be a TPS report about Ford cars and 4 hour idles doing harm. Then there would be a kit on Ebay with a fan and resistors that makes your car idle longer..lol
Hmmmmm....$$$
