amsp is right. Profesional models from real agencies are really profesionals, and the higher you jump in the level, the higher the profesionalism is. No fanfare, just people working.
In my experience, the most reputated models have always been the more friendly with me as an assistant, no complains of any means on set, job done very well, while yes at lower levels you can find hassles
and posing but it does not last very long and wanabee girls who are playing this (arriving late, complaining, etc etc...) would be rejected and their carreer soon ended.
Now, on "managable", they are, but the photographer has to be at the same level. It's like if you want to ride a race horse, you need to train first with less "difficult" animals.
In any profession at the high level is the same.
In fact, the really profesional models are among the nicest person to work with I ever met.