This is well underway now in the Premier League.
Half the time, I don't know why the club does it.
Julien Lopetegui has just got the bullet from West Ham; and was having to take training knowing that the club was talking to his successor, Graham Potter.
West Ham, be it noted, let David Moyes go at the end of last season because the fans didn't like the football his teams produced.
Or Russell Martin at Southampton, who scraped into the PL via the playoffs with a squad which is nowhere near PL standards.
What do the owners and fans of these clubs expect? How are West Ham going to compete with the monied clubs of Man City, Arsenal etc?
With great difficulty.
With the squad that Southampton have it would be a big surprise if they stayed up.
I'm not saying never sack the manager. But some are replaced (sometimes at great expense) by another manager who is no better and given the players at his disposal, would have to work miracles to produce success.
ETA- since I posted this, Everton have sacked Sean Dyche!