Don't be fooled into thinking that since a trailer/fifth wheel is new, the factory got it right with amount of grease or axle nut torque specifications.
If you do a search on bearings on this excellent forum, you will see sometimes the factory failed to put enough grease in the bearings, hubs, or over-tighten the main castle nut, which happened to me.
One of my axle castle/axle nuts were on so tight it took me and my adult son, along with an long handle on a wrench, to break it loose.
Had I not checked and caught this condition, no doubt the outer and inner bearings would have failed, leaving me and my wife on the side of the road or worse.