the trick that they use is writing beyond that, six months to a year out, allowing for the in and out of actors, not as in permanently but in things like vacation time, plus the need to resource in all they need to underpin the storylines.......I have been involved on the fringe, writing in long term scenarios - I would love a go at writing the screen play, though that is very different to my normal literary writing (and outside the bread and butter of the tech work I put together).
It's fun and what this Ed has done is to push me to develop.....partly as I have discovered that I can write pretty cleanly, i.e. not massive proofing needed (after spelling and 1st line editing on Word - and that is done here, well not on AB...lol).