I can't see ten Hag being given the time necessary to get United playing the way he wants - they'll start off with good intentions, but panic when there's no sign of improvement after 18 months.
I think Utd have been patient with their managers, the problem has been their decision making on why were they.
Jose played the shittest football they have seen in years, their fans hated it and complained about it but they stuck with him, let him spend a fortune and let him pursue down a road that only teams like Stoke and Burnley were happy to be playing. With every passing week, they were moving further and further away from where they wanted to be but the Club were blind to the path they were on.
They repeated this with OGS. I think he was the right man as a placeholder/interim coach. He heeled the fanbase to a degree and the results picked up even if the performances didn't. But they gave him a contract!!! When instead they should have been looking for an elite manager (and looking to rebuild the club behind the scenes like their recruitment dept, academy and plan more strategically behind a vision of how they wanted to be in the future).
We could go further back too but they did chop and change with Moyes then Van Gaal.
They haven't had the football knowledge to know that they have been heading in the wrong direction for ages, they repeat the same mistakes over and over again. They have enough individual talent in the squad to pull out improbable results, the classic example was when we played them. We outplayed them the entire match but on that day Ronaldo did what he's capable of doing (but not sustaining, which is why he doesn't do that every week, if ever in the past 5yrs or so in his career). That game was a microcosm for what they are built on, which is sand, and why we finished 13pts higher than them with a GD 29 better too.
If they had any football knowledge in the decision-making seats then they wouldn't have hired any of these managers in the first place, let alone hung onto them and let them build a team buying whatever big name footballer happened to be on the market.
Time should be afforded to managers who are clearly making the team play well, better than the sum of their parts, playing to the managers' instructions by demonstrating repeatable patterns to their game. Even if they aren't getting results (see Poch's first season, see Klopp's first 2 seasons, see Pep's first season).
Most fans can buy into a journey, and as Woolwich have proved even buy into a manufactured journey. At no point since Fergie leaving have Utd been on a journey, it's all been about individual moments delivered by a world-class player doing something every 4 games whilst adding nothing to the team in the other three.