Just to clarify my previous post, on the B747-400 the Stab tank will start to transfer when the Centre tank is down to about 36,470kgs of fuel. As Lancer says, the CWT is the first to feed , if the Stab tank doesn't transfer then you will need to find somewhere to land before an out of trim situation develops.
To say it will be burnt by TOC isn't very helpful so I have edited that bit out, that is what frequently happens but is a factor the total fuel load rather than how the system operates.