The head gasket

Without an aggressive maintenance schedule on the engine cooling system, the head gasket on today's vehicles will last between 10 to 15 years at best.  Sometimes shorter if lots of short trips are the norm.  Corrosion is the enemy.

The best thing you can do to reduce corrosion eating at the head gasket is to reverse flush the engine cooling system thoroughly and change the coolant before it is due to be replaced.  This does three things:  Reduces the amount of particulate in the cooling system that raises the electrolyte level, renews the lubrication properties of the coolant so that the water pump shaft seal is conditioned and has less chance of failing, and assures the right specific gravity is maintained for freezing temperature protection.

To test the level of electrolysis of the antifreeze in your car you will need a voltmeter that can measure 0-1 volts.  The easiest way to measure it is to wait until the engine is cool.  Remove the radiator or coolant cap.  Put the positive probe of the voltmeter in the coolant without touching anything but the coolant.  Touch the metal on the radiator with the negative probe.  If the reading is between -.3 volts and .3 volts, the coolant is healthy.  If the reading is beyond -.3 volts or beyond .3 volts, the cooling system needs to be reversed flushed and the coolant renewed with new coolant mixed to the right proportions.  Keeping the voltage between -.3 and .3 volts is the best way to make that engine head gasket last as long as possible.

And of course, don't let the engine run out of coolant because of a leak.  Overheating is very stressful on head gaskets. : )

If you cannot or do not want to check the voltage of your coolant, have your mechanic do it every time you have your vehicle serviced for regular oil and filter changes.