Right up there with death and taxes on the inevitability scale is an enormous TV rating for the NFL‘s annual championship game. Advertisers, of course, are hip to that — and Fox announced today that its ad inventory for Super Bowl XLVIII on February 2 is completely sold out, nearly two months before the Big Game. Sponsors are shelling out an average of $4M for a 30-second chunk of the prime airtime during the game — one of the few remaining events most TV viewers watch (gasp!) live. Some late spots scooped $4.5M. By contrast, CBS didn’t announce an ad sellout for its 2013 Super Bowl until January 10, when 30 seconds was averaging $3.7M-$3.8M. Fox Sports Media Group EVP Sales Neal Mulcahy wouldn’t divulge exactly who bought which spots for the game, but he noted that there’s still some ad time available during the postgame and endless pregame programming.