basic attack deactivates

it depends on the class. I always just keep hitting the hot key. By default it is "1" unless you moved it.

You should be in "combat" state for keep attack white hits. For example, if you doing weapon training on the gates in sw, you need to aggro baloon on you but don't kill it, and then target gates and hit "attack" button. Or use warlock+pet or any other tricks to keep "combat" active.

I agree with Justuser that I can see my rogue classes just keep going. There is a second or two between hits. I think it depends on the weapon speed. The lower the weapon speed, the faster it repeats the attack. I have seen even my priests and mages repeatedly smacking the target with a staff once it starts. Maybe you need to wait and see what it's doing.