It is a sealed tube so the leak is all outside the wall, but since the repair amounts to removing the plate, unscrewing the diverter, and screwing a new one in, why wait with the repair. When it reaches the age where it leaks, one of two things usually happen.
1. It starts sticking so you have to pull it out after showering, or
2. It breaks and that pin "shoots" out, often striking a delicate part of your body.