This thread brings up an issue which I have heard raised in similar contexts before: that of people being posted every two years.
I've heard people say that it causes hiccups in the management of projects and facilities, it costs a fortune in terms of resettlement payments, it affects the kids' education, causes family upheaval, etc. One person - a reasonably young-looking female flight lieutenant involved at the time in recruiting - told me that spending six months of every 18 either moving out or moving into another home was absolutely the single worst thing about being in the RAF.
So why do it?