As a colleague has stated to me; he simply cannot afford to waste half of his working life to end up with a £7000 per annum pension - and that's if the goalposts don't move between now and then.
Hence his initial 6yr ROS is coming up and he'll happily take his 1200hrs, multi-jet and poke off.
Another colleague would rather take his pension and work in McDonalds rather than keep destroying his family life.
For guys of my generation, 35-42 seemed to be about average leaving ages. Now it's more like leave as soon as your initial ROS is done. So depending on holds and joining age, that could be anywhere from 27-30 yrs old.