2-3 years is fine, though it mostly applies to clubs that are already relatively stable with a good squad rather than one in relative crisis. For a club like ours I'd say 3-5 years is ideal. Imagine if Klopp had left in 2018. If only eh.
Either way, 12-18 months is a disaster, there's no way around that fact. It points to a club that has no idea what it's doing or what it wants to do. United are actually a good example that patience can have a positive impact even under a shit coach, because you'll at least end up with a team that's SOMEONES vision rather than this unholy cocktail we've ended up with. If they hire a good coach at the end of the season that's a team that can actually go places.
Also the narrative that Arteta and Edu have made things much much worse is completely false. You'll hear some blurt out that Emery finished 5th, yet completely ignore that when Arteta took over, the club had won 7 of it's last 25 league games. To put that into context, we've won 10 of our last 25 league games under Arteta. You can want him out for various reasons without pretending like he and Edu have plunged us into this.
