It could be that M & S are hired by RLC meaning they are in EU on a working visa which are valid for much longer. I suspect RLC keep the Barcelona on a rotation on purpose by not hiring the girls, they are there on regular tourist visas (or whatever the non-work ones are called). Personally I think the rotation is a good idea, makes the apartments interesting in the long run. Sure, sometimes you lose a girl you really like but you also get rid of the ones you like less.