Well, while it technically has nothing to do with the servos, it does have to do with the FS position, at least on spektrum. So if you don't get the new servo (especially t/b servo) in the exact same spline/position when you reinstall it, if you lose radio, the FS position may be off.
Usually, any time I take a horn off a servo, I rebind to make sure the FS spot is set where I want it.