In my opinion doing oil changes more frequently than factory recommended intervals is beneficial to the longevity of your car engine. I usually recommend you do oil changes twice as often as the factory recommends, depending on the model and year of your car.
Often you see flyers or advertisements for very inexpensive oil changes. These ads usually say the oil is synthetic. BMW always recommends you use synthetic oil depending upon the application. So people usually figure this is a good deal that may save them money. In the long run it may cost you more. Although they state the oil is synthetic, the type of oil used on these low cost oil change deals may not be the kind of synthetic oil your engine requires. To use the right type of oil would cost them way more for the oil then the whole oil change job.
I tell all my customers to avoid this as it can cause premature engine wear. Also the oil filters used are substandard filters that can fall apart and clog up the oil supply to the engine.