Regular servicing will prolong the life of your car or van.
Oil is the life blood of any engine or gear box. Keep it clean and it will last longer.
Cambelts should be checked at regular intervals. Replacing a cambelt is cheaper then replacing an engine or cylinder head.
Coolant should be checked on a regular basis. Low coolant or old coolant can lead to head gasket failure.
Tyres and brakes are the most important of all. Making one ton of steel propel itself to 70 mph is one thing. Making it stop safely afterwards is another thing entirely.