This was always to be expected if things did not start well; but anyone suggesting he may not last long will have to explain how a club that has taken such a long-termist view of management in the past should suddenly start to hire and fire like Roman Abramovic.
Given that Moyes was Sir Alex Ferguson's own choice as successor - making him effectively his final signing - it would make no sense for one bad run to prompt all that extensive succession planning to be ripped up, with no clear plan in place over what to do next.
Indeed, Fergie himself provides the clearest reasons for persistence.
Imagine being placed in a time machine and transported back to 1986, when Fergie took over. You could say plenty then to Manchester United fans, rival supporters, commentators and anyone else with an interest. What fun it would be.
"Will Fergie bring success in the next couple of years?" they will ask.
And you will tell them: "He will stabilise the team this year and the side will rise to second in the table in 1988, with club legend Mark Hughes being re-signed the following summer."
"Ah," they will say, "so glory will not be far off?"
And you will tell them: "What happens next is the team stumbles, sliding into mid-table, winning nothing, then spending heavily in the summer of 1989 without any clear improvement to show for it. The club finds itself in turmoil as a takeover falls through. The team will get thrashed by City in the derby and be sliding towards the relegation zone. By the end of 1989 there will be chants and banners calling for Fergie to be sacked, with the team drawn away from home in the third round of the FA Cup against the best cup team in the country."
"Oh well," they will say. "He can't possibly survive in that situation. What a pity - he was such a success in Scotland."
"But no!" You will reply. "Under Fergie they will not only win that cup tie, but pull clear of relegation, win the FA Cup and go on to enjoy the most successful period by far in the club's history. They will not just win the league, but win it time and again, including two championships hat-tricks and three league and cup doubles."
By now your audience is looking somewhat wide-eyed, but you keep talking..
"Ten years on from the low point of 1989 they will win the League, FA Cup and European Cup in the same year, then become world club champions too, and Fergie will get a knighthood for it. That won't be the only time he leads United to the European Cup, and when he does finally leave he will do so on his own terms with another championship trophy in his hands, having been boss longer than Sir Matt Busby, and having chosen his own successor."
At this point, of course, your audience will conclude that you are not a time traveller, but a complete lunatic - and have you carted off to the nearest mental hospital.