Any chance there's a local community bike shop that has used coasterbrake cruiser wheels?
I'd be looking at finding an old Bendix coasterbrake rear wheel. It's going to be harder to find, but if they're in good shape they'll out live your Cranebrook. This doesn't preclude needing to regrease and replace the retainer bearings, all hubs with loose balls need this kind of maintenance schedule. Short of doing that you need to make sure your Chinese CB hubs have enough grease inside them. I'd go with Hi temp disc brake grease, and get some help getting your coasterbrake bearing adjustment correct, hub turns smoothly and freely with not cracking and (or) grinding feeling or sounds, and that the lock nuts both tight before re-installing the wheel on the bike.
