I don't know what the rules are for long haul flights and F/A staffing requirements.
It would seem logical to have more than one F/A crew on a 12 hour flight because the F/A's would need time for breaks. If you need 7 F/A's for a 347 seat 747 than you would need extra F/A's to cover coffee breaks and F/A meal/break times.
Isn't there also a lead F/A that's more of a supervising F/A on long haul flights?