Re: Sometimes I think grease fittings on bearing hubs should be outlawed
For my many RV/TT trailer, Utility and boat trailers, I use Dexter brake hubs (which are high quality compared to other brands). Yes. I even use Dexter brand brake parts on my boat trailer.
As per Dexter, their magnets & inner hubs parts must be inspected every 6 months. And to inspect these inner hub parts, one must physically remove the wheel hub. And if one physically removes the wheel hub, then "by default" they are forced to manually check seal conditions (replace if leaking), bearings / races (replace if needed), magnets (replace if needed) and end caps (replace if necessary) as well. To view official maintenance schedule, surf:
http://dexteraxle.com/i/u/6149609/f/Service_Resources/Maintenance_Schedule_1-12.pdf
Since I don't do RV/TT camp or do boating during harsh winter months, I do trailer hub maintenance every 12 months (since trailer is parked 4 months of the year). And, always in the spring - to replace natrual moisture that forms during temp changes winter / early spring months.
Folks encounter wheel hub problems (especially hubs with grease zerks) because they simply squirt/squirt every 12 months and do NOT pull the wheel hubs off - for proper inner hub maintenance tasks (based on maker's formal maintenance schedule). They only remove hubs AFTER a problem happens. Which is often too late. Yet, these same people replace Tow Vehicle engine oil and Tow Vehicle Transmission fluid "on maintenance schedule".
IMO, I also feel wheel hubs with grease zerks (or simular self lubrication systems) should be illegal. Thus, making trailer owners perform proper maintenance (re: 6-12 months intervals) on their wheel hubs. re: They are forced to remove the wheel hubs every year and proactively fix / replace - which needs to be fixed. And when the wheel hub is off, they can visually confirm no internal grease leakage (from leaking seal) as well.