Dunno if it's true or just scare tactics, but when my car was in for it's cambelt change the other week at the dealers, at about 4 and a half years, the service desk were telling me that they have seen a few belts recently that have let go.
And caused no end of damage. This was while it was in, so they were not trying to sell me the cambelt work.
Guess these were on a mixture of cars that were older than 4 years old, but that's what I was told.
They gave no specifics so this could all be BS, but that's what was said.