The kicker for me is that it IS a contract. Any downturn, direction change or political machination and you are out.
I have several friends who were at Sing-air, one of the best ex-pat gigs-right up until they don't need you any more, then the round-eyes are gone.
If it's a case of a few years to finish up and pay off the yacht before hanging it up, great, but if you need another decade plus of income, I'm loath to bail on what's a secure job.