It's also important to define what the project is, the issue with the supposed project is none of us know what the criteria is. If the project is to win the league or challenge in four or five years the teams trajectory has to be consistently moving forward which by rule isn't being witnessed this season.
I see Arteta mentioned so often in these conversations but there are too many differentiations between the relativity of Arsenal and United, a United manager would not last two consecutive 8th place finishes point blank period. Arteta is certainly an exception to the rule because if he was at Liverpool, City, Barca, Madrid or Bayern he would have been sacked. It's also imperative for critical thinking sake that he's not won anything of significance at Arsenal so while it's completely understandable to acknowledge his development from A to B history won't account for it no different to how no one accounts for the brilliance Poch showed at Tottenham (until Arsenal win something of note).
The most relevant scenario to objectively view a managers progression at a club of substantial size and resource, is to look no further than Klopp: 8th, 4th, 4th, 2nd, 1st with a UCL final and win two consecutive seasons in a row. That is how an unproven manager buys and builds credibility at a big club. Multiple things have to click in place including perhaps the biggest which is fantastic recruitment. That's not even touching the ethos of the manager and his ability to coach the team which is fundamentally what's undoing EtH tenure in his second season at this moment in time.
So while time is certainly a requirement for any manager there has to be a linear show of definitive progression (should be easily comprehensible) for them to earn there stay, not a lateral trajectory of development.
