The problem with most people and oil changes is, they see that it is recommended to change every 3000, 5000, 7500, 10k 15k, etc but people neglect the FILTER. You should still change the filter every 3-5k at least!!!
Also, as has been mentioned, many of the recommended oil change intervals are for regular driving which consists of zero stop and go/city driving. For best results, get an oil test on your oil and determint the proper interval from that or just keep changing it more frequently such as 3-5k.