squize: its a bit of a catch 22.

have all the enemies there, running through their enterFrames (checking to see if they are visible or not), being invisible when they are out of the screen.

or

attaching them when you need them.


Personally I dont think their is a right or wrong.. the last platformer I finished (finished being the word hehe) I attached them when needed, and I did see a performance boost.. I think flash still draws a larger area if there are invisible clips.. who knows.. maybe we can get an answer from macromedia...