If you aren't receiving any updates, I'd recommend calling Tesla Service. Sometimes updates will be blocked on a vehicle, and this block can be lifted by the person on the phone. For example, if an update returned an error, they may block the vehicle from further updates. This happened to me once, and after the call I got the latest update within a couple of hours. The tech acknowledged that I had been blocked due to a technical issue with a previous update attempt. Worth a shot if you really are falling way behind. Especially if you didn't get 50.2, which seemed to be a Christmas present to everyone.