One of my lyco 360s generated a small amount of metal in the fine strainer following a bottom end rebuild. General engineering consensus was to keep an eye on it. It did this for 300 hours when rather larger bits started to appear. The decision was taken to withdraw from service and investigate. The centre main bearing had failed big time - no white metal left and it had scored the crank. There was no other major damage. The only other symptom was sparkly bits in the oil when viewed under sunlight. Performance and oil pressure were normal throughout. Cant have been too far off catastrophic failure.
Dont ignore sparkly bits in the oil!