Trailer wheel bearings

Had a call from the yard this morning to tell me that another wheel bearing had gone on the blink.

Just 3 weeks ago I greased the bearings and they all seemed ok. So in the car and a  one hour drive to get there two hours and $53 bucks for grease and bearing save caps to fix it then another one hour drive home. Still the poor old trailer is dipped in salt then sits in the yard for years at a time so what to expect