also I try to avoid the"wood screw" type and use "sheet metal" type servo screws....wood screws are usually triangular shape all the way down to a point...meaning once/if it loosens just a bit, I will get looser even quicker because of the triangular shape...while sheet metal screws are more parallel all the the to the point , so there will always be consistent friction against the threads....

...and even still it does not hurt to add a drop of canopy glue to the threads..easily comes undone with a jolt from the screw driver...my feeling is most servos should last the life of the airplane, and you will not be messing with it until maybe 5 years from now, if the plane lasts that long