The line at the one near my house is almost always long and it's been there for years...
The only time there hasn't been a significant line at the Indio store was Christmas Eve about five years ago....wifey and I had gone to her Christmas Eve Mass at 4:30 with plans to eat at one of the local Mexican places afterwards.
Each potential spot was closed as we worked our way down Highway 111.....yet we pulled up to In-N-Out and voila; not a car in line. That turned out to be mama's very first Double-Double, and she's been a fellow fan ever since.