For further historical context:
Benitez was sacked after taking 5 points from his last possible 36. Mike Walker, surely the most obvious comparison to such a shocking run, was terminated after a run of 7 points from 36 in 1994. In 2002, Walter Smith was finally punted after taking 7 points from his last 36.
So, different eras but very similar patience metrics. The 12 matches that preceded their eventual sackings yielded between 5 and 7 points for all three of these managers. In worse news for Lampard, Roberto Martinez managed 9 points from his last 12 games and still got the bullet. Marco Silva picked up 10 and Ronald Koeman 11 (though three of those points were from the end of the previous season). Big Sam actually took 18.
Allowing for a certain amount of goodwill, Lampard might be given a little more time - Martinez and Silva had had full seasons before being sacked. But let's not delude ourselves. If the board might stomach 2 points from a possible 21 - or even the time-honoured red alert metric of 6 from 36, I suspect that would only happen if there were three or four other sides in similar to worse situations. The real danger, therefore, is that we get cut adrift while going through a horror run. That would, if history is any guide, be terminal.