There is no reason to 'detach' the servo, in fact the detach command is more often used in error then for any valid reason.
But, OP says that they are noisy when holding still (hard to believe) and consume current (easy to believe). So detaching and powering off would address both of those issues.
But, only if the servo is actually powered off, which detaching does not do. The power to the servo would need to go through a transistor that the Arduino turned on and off, in addition to detaching the servo.