Bearing burn out is all to common on RV and boat trailers. Since the reasons are not well quantified, I would highly recommend routine maintenance by a competent service organization if you are not doing your own. Some of the reasons are improper preload on the bearings(too loose/tight), over loaded axles(common problem with RV), incompatible grease(common problem with easylube), grease aged (the reason to repack yearly), grease contamination (common problem with easylube), water (common in boat trailers), improper grease for application and etc.
As mentioned it is a good idea to check the hub temperature periodically while traveling. If the hub is too hot to hold you hand on for 30 seconds would signify that the bearing are running too hot. Applying the brakes create heat so do that when there is limited brake application. IR temperature device would be helpful, but requires a little experience.