My Al-Ko axles have the same system, although with a different name. I did the greasing via the zerk fitting for the first two years, and would have done them another year, but had to replace the springs, and decided to replace the brakes too.
The seals held up nicely, no leakage past the seals at all.
My only suggestion it NEVER use a power grease gun, use the hand pump.
Trailer: Lifted 228BH, heavy duty springs and Yokohama tires
TV: 2016 GMC Sierra Z71 4x4 CC, SLT
Spare TV: Two Alaskan Malamutes
Living somewhere in ID; previously lived in Moab UT; previous to that, don't ask!