It is worth having switched on if you watch a lot of material with letterboxing or pillarboxing - I have mine on 1 minute and maximum shift both horizontally and vertically - if you have kids who watch a lot of 4:3 SD channels and leave the TV on for hours, it does help.
One thing to remember is that it only works in the 16:9 and other ratio options but not in screen fit. This is because all the other options are overscanned and have pixels around the edge to move. Screen fit however is a 1:1 pixel for pixel screen map, so has no extra image around the edge to move.
Whether it will lessen your image retention depends on your particular screen, but it can certainly do no harm, and even if you see it working, you do become oblivious to it after a while.
Rob