The capacitance will add up.
The capacitance will add up. The reason why you want a separate capacitor near each of the servos, instead of one big one, is that when the load on wires is changing, the wires themselves also become an electric element – they become a coil. And together with a capacitor you get a nice RLC circuit (https://en.wikipedia.org/wiki/RLC_circuit) which will do Bad Things™ with your current.