If you can, yes that is a good idea.

Have the servos powered by that battery pack.

This way if there is binding or a problem with the retracts, they will not consume your flight pack's batteries.

Note that some retracts do NOT require "retract servos". It really depends upon your plane and TX.

Retract servos move to two somewhat fixed positions. This is great for retracts that use an interconnecting wire to drive two retracts off a single horn or horn/wheel. In some cases retract servos may be mandatory.

However retract servos not be necessary for retracts driven off a single servo, where you can control the end points and movement of the servos via a computer controlled TX.

I have various planes that use inexpensive standard non-retract servos on the retracts. All operate w/o problems and with newer TX's you can control the movement speed of the servos to get very realistic retract movement... You can't do this with retract servos.