Interesting time for older managers, you've got Harry Redknapp, Sam Allardyce, Roy Hodgson, Steve Bruce, Ronald Koeman + a bunch of others who are out of job and possibly won't manage again,
Times change and people get older but usually there's one or two managers coming to an end, where as in the last year there seems to be a lot of managers who have left what will probably be their last job, sad times.
I've never been convinced by Koeman's man management but I have always been impressed with his knowledge of the game during interviews.