ive seen 3 or 4 of them go to oblivion, thankfully not on my own car, but the first one i sorted totally wasted the valves as the guy kept driving it with no tension on the belt and it inevitably jumped , the second one the guy stopped str8 away when he heard it start making a racket and we got away with a new belt and tensioner after finding every single bearing as they had all gone behind the bottom pulley etc. right kerfuffle.
definately worth changing, as these were on standard engines not being given any stick.