Im not really sure with your statement however arsenal dont really need to change their manager because arsene wenger has been consistently keep providing arsenal with atleast the 4th rank every season and he only spends a few pounds in getting new player every season. In management aspect, this is totally benefical for the club and there is no reason to change him for sure
yes it is true that arsenal got benefit from arsene wenger managerial, they dont spend a lot in buying player instead they are trained junior player become big player, but we are missing the moment where arsenal compete for the championship
That may be good for the club, the manager just spent a little money to get a talented player and turn it into a great player
but that's just for the club is not for manager, a manager considered a success if register his name in the history of the club won some trophies and Arsene Wenger need it before deciding to retire.