Oil change light, time or?

What would you listen to? The "oil change needed soon" light in the car, the time between oil changes, the mileage or the service writer? I have a Ford & use Motorcraft full synthetic oil. It's been just over 6 months, 3,700 miles & the light turned on to change the oil. My service writer is great but he's telling me to wait for 5K miles, I'm wasting my money. I appreciate him wanting to save me money. I'm thinking go by the oil change light. The car is programmed & knows what it wants. There's nothing more important then the oil. Your thoughts.