I always tried to look after the engine as best I could, and that meant the power reduction to idle at TOPD was done quite slowly to let the temperatures change nice & smoothly.
It won't hurt the engine by chopping the throttle to idle but it can't help the longevity of them. (if that makes sense)
Same deal for when I used to fly little turboprops around - when taxiing in after landing I'd try to keep the power changes to a minimum so as to keep the temps as low as possible for as long as possible before shutdown.