Replace the Thermostat as Part of Regular Maintenance
In my opinion, replacing the thermostat is probably one of the most overlooked maintenance items. I mean, who really worries about the engine's coolant thermostat? True, the thermostat isn't something that needs to be replaced every 3 months or even on a yearly basis, but it should be replaced...
...How often should you change it? In my opinion, at least once every 30,000 miles or every three years (at the most!). Considering the importance of the thermostat in keeping the engine at the correct operating temperature, this little item should not be overlooked in preventing the engine from overheating!
If the Vehicle Overheats on the Road
Most of the head gasket repair jobs that have been assigned to me (at work over the years) usually resulted from the customer noticing that his/her vehicle was overheating, but decided to drive it as far as it would go. A thousand dollars plus later, he/she realized that maybe it would've been better to pull over in safe/public place and have a tow truck tow it to the shop.
There are so many factors involved in deciding to pull over and have it towed home or to the shop, when a vehicle overheats. Things like: Is it a safe area? The weather (rain, snow, cold, heat, etc.), how far you're from home, etc.
But, once your vehicle starts to overheat, every mile further down the road you drive it... is possibly adding more money to the final repair price. Not only that, the engine will eventually just stop (stall). So it's better for you to decide to pull over in a safe, public and well lit place and wait for the tow truck, than to have the engine blow a head gasket and quit on you in the most inopportune time and place.
Maintenance is Key to Preventing a Blown Head Gasket
Maintenance involves time, effort and the five letter dirty word: money. There's just no way around this but considering just how expensive it is to have the head gaskets (and possibly the cylinder heads or worst case: the whole engine) replaced... the cost of preventive maintenance is far cheaper.
Remember, it is possible to prevent a blown head gasket on your Ford 3.0L or 3.8L equipped car, pick-up or mini-van if you check for coolant leaks, repair coolant leaks as soon as you spot them (avoiding stop leak in a can fixes), replacing the thermostat as part of routine maintenance, and if your vehicle does overheat... stop in a safe place and have it towed home or to the shop.