I had the same problem last year. I was less than 100 miles short of GM because DL kept cancelling flights I had scheduled in December. I didn't make it. Given the circumstances, I asked that my GM status be extended, but I never got a response. Fortunately, DL ran one of those GM promotions i.e. so many segments/miles by 3/31 and I requalified. There are a ton of cheap flights out there--just grab one.