all our recent trailers have had them and the 2001 boat and trailer is still on its original bearings despite having been all round the country to different venues and now sitting for long periods of idleness as the other boats do its job. I think that the main solution however is good waterproof grease. Some are not and form an emulsion with seawater within which the bearings happily rust away. We used to use castrol heavy and never changed another bearing after starting with it-but no longer available. Now as for *!*!*! brakes that is an entirely different matter
although we did manage to get some brake cables with a grease nipple halfway along last time and they have been bril.