if you look at Madrid, it's hilarious. Ramos, Higuain, Pepe and Marcelo were meant to be part of a new wave of young players to carry the team forward. and sure enough they won a couple of Titles and it looked like Madrid were set for a long long while. they had so many quality young players: Sneijder, Robben, Robinho, Gago, Garay, Drenthe, Huntelaar, etc. etc. etc. - but then we showed up and smacked the fuck out of them, so Madrid aborted their young squad in short order and started on a new one. they should have just kept building on their current effort, but ego and douchebaggery run deep at the Bernabeu.
it's worth remembering, also, that while there are 4 survivors from that aborted mid-decade team, the club has until this summer tried repeatedly to ditch 2 of them (Higuain and Marcelo). and they were constantly trying to find a new defensive star (Vidic, T-Silva, etc.) to move Pepe to the bench.
they are an ugly club with an incredibly high rate of player turnover.
the only thing that may slow that rate down is the fact that they spent such an ungodly amount of money assembling this current squad (€30m for a backup utility man with no real place to break into the first team down the line) and won't have any to buy new guys unless they sell first.