I have never heard of extending a filing deadline like this, dj; is it legal to do so? LA would not extend the Democratic filing period when Allen Ellender died while campaigning for a sixth term in 1972. But that deadline had passed some weeks before.
Laws vary from state to state, obviously. I personally think it is ridiculous that the period to file is a year before the election. Primaries should be in the summer of the same year of the election and the closing period less than a month before. Shortening election seasons will get us away from this endless election cycle.