Frequent oil changes do help to prolong engine life, but only if a good quality oil is used. A fully synthetic oil such as Mobil 1 will almost certainly have better film strength after 10,000 miles than conventional mineral oil when it is new, so frequent oil changes with a cheap oil are probably a false economy. Oil is also intended to get 'dirty', as that is how it removes combustion products, so a bit of darkening is to be expected after several thousand miles
However, one important point that nobody has mentioned here is driving style and 'mechanical sympathy':
As an example, racing engines must be warmed up carefully, as the oil must be warm to circulate properly, and tight fitting pistons can seize in their bores if they are heated up more rapidly than the cylinder block. (Note that racing engines tend to use single grade oils rather than multigrades). Any metal to metal contact between moving parts also creates heat, which cannot be carried away quickly enough by cold, slow moving oil, and may result in scuffing or seizure. Much the same applies to the large diesel engines used in ships and railway locomotives, which must be warmed up before being put under load.
The small engines in private cars are less prone to these problems, but all the same, thrashing any engine from cold will wreck it, no matter how good the oil is or how often it is changed.
If you really want your engine to last the following should help:
Always allow a cold engine to run at fast idle (1000 RPM for the V6) for at least a minute or two before putting it under load. This is especially important in cold winter weather.
Drive the car gently (as if it is running in) until the engine is thoroughly warm. In the case of the V6 Omegas this is only three or four miles. However, if you live on a fast main road, and cannot drive gently for the first few miles, it may be a good idea to let the engine warm up for a few more minutes before driving.
Avoid driving at constant low speeds. Driving at a constant 56 MPH may save a bit of fuel, but over several thousand miles the cylinder bores will glaze.
Similarly, don’t allow the engine to idle for long periods of time. This is especially important for diesel engines, which will suffer glazed cylinder bores and high oil consumption.
Turbocharged engines should be allowed to idle for a minute or two after fast driving to allow the turbochargers to cool and run down. Shutting down the engine too quickly can leave the bearings without oil whilst the turbines are still spinning at high speed.
NN