Purely guess work here, but the last build lasted 2 yrs or so & cost god no's how much, looking around Shaibah it self there appears to be load of building work, so I guess they are in Shaibah for at least another 2 to 3 yrs plus
Go onto your Google earth and have a look at the work going on at the APOD. You will see camps going up, thats not for theatre expansion, and you will soon see camps coming down at SLB. The Hosp is one that will soon be down.
Your right the British are in Iraq for more years just not at SLB.