As others have said, it depends on the type of driving you're doing. You can push your car past 3000 miles if you're not putting a lot of stress on the engine - and by the same token, if you -are- putting your car under a lot of stress, you may want to change your oil even more frequently.
I confess - I've pushed my car past 3000 miles on a few occasions, by adding some more oil on my own to hold things over until I can get the car into the shop. (At this point, my car is so old that, if things got so bad that I'd need to replace my engine, I'd replace it and get a whole new car to go around it
)