"Can anyone explain how these operating bases work ?"
Quite simply, they only work short term. They start a route with the 330, six months later the 777 fleet or Southwest division decide they'd like to fly there & your base is shut. Note that these decisions are not commercial but political and rarely make sense to westerners. And you'll find out through your own sources, not from your employer. You can now fly from another base at your expense.
Their track record on A330 base closures is impressive - Munich, Frankfurt, London, half of Sydney, attempted Vancouver, attempted Melbourne, Milan. Each base closure results in an oversupply at an adjacent base with a resultant decline in scheduling for all (read as an effective Beijing base).