If I am correct you are talking about a Motorhome, not a trailer. The rear wheel bearings are taken care of by the rear axle gear oil, no greasing involved there. The front wheel bearings should be good for a lot more than 16,000 miles, but refer to the specifications for the manufacturer of the chassis. I presume Mercedes?
2020 Eagle HT 30.5 CKTS (16" wheels, spring shackles set on lower hole of frame, standard kingpin, B&W Companion slider)
2019 F250 SRW SuperCab 4X4 SB 6.2 (10,000# GVW) 3.73 Axle 18" wheels