Greatest Number of PP Operatives?

What sort of numbers of operatives do people use as they progress through the game?

-one large team of 8ish only?
-a team of 5-6 at each PP base? (Has anyone actually managed/tried this?)
-3 teams of 6-8 covering most of the world?

Can a team at each base be feasible? Can each base support its own growth and equipment?