Diego Simeone has been managing Athletico Madrid for nearly 700 or so games if I am not wrong, which is quite a lot and something we do not see that often anymore, because most teams just change their managers like they are changing a sock so we do not get to see this many teams with the same manager all that often.
A coach staying very long in a team is good but there ought to be a limit that will based on the achievements of the coach and the progress they gave made as well. To me a good coach should be able to prove himself within a period of five years. Diego Semeone is a good coach no doubt, but the results he has achieved in Atletico Madrid, in my opinion, is less than expectations and the name of Atletico Madrid. I remember he has lost Champions league final about twice which is 2014 and 2016. This to me is not a good one and if I were to be the management of the club, I would have tried another coach.