It depends on how you drive. If your car always (or nearly always) gets warmed up, and you don’t drive it very hard and keep the revs down, the manufacturer’s recommendation is probably fine. If, however, you drive it hard, drive it at high revs, or alternatively, if you only drive it to and from the supermarket so that it doesn’t get up to temperature, then you may wish to change oil much more often, perhaps at 3000 mile intervals (given that most manufacturers are now specifying 7500 mile intervals.) If you don’t drive your car much at all (about 7500 miles a year), then you probably want to change oil every six months anyway. If you are storing a car during the winter, then change oil before storing it and change oil when you bring it out of storage.