Not an expert in this field at all.
There ks a trailer shop in Silvertondale in Pretoria called roadque, sur they would be able to give you good advice.
Went to Sodwana over the weekend, passed a couple of trailers and boat trailers on the side of the road with bearing problems.
My advice, if your boat or trailer will be standing for long, put it on tressels, and service before any long trip, just my 2c, but being a boatowner, I am sure you know this by now.
Regards
B