Bought our Chevy (see signature block below) a year ago. I had to add DEF after the first 2000 miles. Then the next 1500. By this time I was getting really worried wondering if this was going to be a costly expense and a horrible truck!
Well, the stretches have gotten longer and longer. I am now at almost 5000 miles since the last oil change and DEF fill up and I still have no warning message.
So, I'm thinking.... there must be some kind of break-in period for this. I know these new vehicles have computers that keep memory and track your driving patterns. It's possible, enough miles are on the truck now the computer has finally figured it all out. (that's only my guess).
But my truck now has about 15,000 miles. Just last week I decided to buy another jug of DEF and have it in the back of the pick-up truck, ready for when the warning comes on again. We've been doing a lot of camping this summer, short and not so short trips, so decided I better be ready when the warning comes on again!
Anyway, that's what I've figured out, it's a break-in period.
By the way, the first fill-up with DEF really threw me for a good loop. We had trailer in tow, on a Friday night. We managed to find a GM dealer on our route. I told them I'd never filled before, had no clue what I was doing. They walked me through it, service guy was really nice coaching me. It took about 4 and 1/2 gallons to fill. Even they were surprised. They said when we bought the truck, the selling dealership probably failed to fill the DEF. There was just enough in the tank when it came from the factory to make it derivable. They said, the selling dealership should have filled it, but it's possible, it was one of those things that could have been missed. This made since to me, and really.... the distances between fill-ups became longer and longer ever since!
Be patient grasshopper. Start tracking the mileage and see if this pattern happens to you too.