Over time the coping and tile that sit on your pool’s bond beam will deteriorate. You can check the structural integrity of your own tile and coping by tapping on it with your pool cover pole, or with a wooden broom handle. The more hollow areas there are, sooner you should schedule your pool for repairs.
In some cases small amounts of tile or coping can be repaired if you have a specific problem area. However, once you have large amounts of failure in the grout and the mortar bed, it makes more sense to replace the tile and coping together so that they are both structurally sound.