The charge against Jose is that he would leave the club after just a couple of years. That's not an unreasonable charge in light of his past, but is it necessarily the case that he would leave United after 2-3 seasons? I don't think so.
Jose can be excused for leaving Porto to take the Chelsea job, right?
The Chelsea job went tits up almost entirely because of their fukked up owner, right? Roman wanted to manage the day to day operations and select the squad, which is completely intolerable for any manager, as we have seen since Jose left.
Jose saw the writing on Inter's wall and can be excused for bailing when he could to take a better job, right?
So far, I don't see a single case where Jose "should" have stayed on with the club.
But now we're talking about Real. I don't follow the daily palace intrigue, but it seems to me Jose has had enough, reasonably so, of a situation that has quickly devolved into a no-win scenario for him. And it's not as though Real haven't churned through managers over the last few decades. While Fergie has been at the helm at United, Real have gone through 24 -- incredible! -- managers in that time. I can't blame Jose for wanting out now.
And haven't we known that Jose desperately wants to come back to England, either to manage United or perhaps go back to Chelsea?
If we got 5-7 seasons out of Jose, which is not at all unrealistic, that should be long enough. Even the tenure of a manager like Arsene Wenger (15 years now?) is virtually unheard of in the modern game.