Engine bearing defective ?

Hello from Manne, can someone give me from you a tip, what one notices that the engine bearing(s) are defective ? As far as I know are the oil-filled bearing, two for the engine, one for the Autom. transmission. So on these three bearings, lies the drive unit. What do I notice when one or two slowly give up the mind ? And after how much km ? Have now 148 Tsd Km down, engine is a 350. Would be grateful for any answer. Greeting, men