Many of us who use our trailers hard (not just boat trailers) inspect, repack, and adjust the bearings once or twice a year. It beats sitting along side the road somewhere doing trailer repairs. Now a good set of bearings, properly packed, if no water gets into them, and if you're lucky can last a long time but, as Dirty Harry Callahan said. "Do you feel lucky?" As to Bearing Buddys. Trailer Buddys, etc.: These additions allow you to fill the hubs completely with grease and a spring in the "Buddy" will exert a slight pressure on the grease and keep out unwanted water. Very handy! However, they do NOT circulate fresh grease to the bearing. The bearing runs in the same grease it was packed in until it is repacked. If it gets hot, and burns its grease it will fail. All the while being surrounded by all that extra grease in the hub. There are systems out there that inject grease into the rear bearing while venting grease out the front of the hub. These systems DO circulate grease through the bearings. Bearing Buddys do NOT.