Ive personally only ever had one spool down in over 2000 hrs, it was a fractured fuel pipe to the FCU. Started in hover but recovered during subsequent descent due to labrynth sealing caused by the airflow past the pipe. Luckily for me i was hovering at 2000 ft at the time so loads of time to recover. The pipe was fractured about 70% of its circumferance.
Another spot of luck was that it was operational so we carried out fast approach and landing as normal. I fear the worst had we carried out a normal sight picture approach.