Well we made it, the bus trip to Trelew was a breeze. I can't really believe it was 20 hours. Here's what i did:
I read my book for a bit
Watched two downloaded episodes of Graham Norton on my iPod
Went to sleep
Listened to some music in the middle of the night
Slept some more
Arrived in Trelew
It was amazing, really comfortable and relaxing. Better than First on an aeroplane (except for the food). I'm now thinking I could do longer bus trips as long as I go Super-Cama or Ejec-Cama. All lovely.