Looking at the archetype, it doesnt really say anything about how long or often you can summon the whips. Is it an at will (albeit as a full round action,) or limited?
It appears to be at will -- which makes sense since this ability basically replaces your Phantom.
That's where I was leaning.
Secondary question: do the usual whip feats work on the ecto-tendril?
They are not "Whips" but are as the ability, "Ectoplasmic Lash," which are basically ectoplasmic noodles of the Light/One Handed/Two Handed variety.
My character, a Changling, calls them "Tentacles."
....and Im officially calling them "ecto-noodles" from now on